TERRY GROSS, HOST:

This is FRESH AIR. I'm Terry Gross. We're going to talk about one of the great mysteries of the human body - how the immune system works. Why does it sometimes attack healthy tissue, leading to autoimmune diseases like rheumatoid arthritis and diabetes? And how are scientists harnessing the latest discoveries about the immune system to create new medications to fight cancer, autoimmune conditions and other diseases?

My guest is immunologist Daniel Davis, author of the new book "The Beautiful Cure: The Revolution In Immunology And What It Means For Your Health." He's a professor of immunology at the University of Manchester in England where he runs a lab that uses microscopes to learn by watching how immune cells detect and kill diseased cells. He says the immune system is far more powerful than any medication we have devised.

Daniel Davis, welcome to FRESH AIR. So you say our body's own remedy, the immune system, is far more powerful than any medicine we've devised. Before we go into detail talking about immunity and autoimmune diseases and vaccines and all that stuff, what is it about our own immune system that makes it more powerful than any medicine?

DANIEL DAVIS: Well, quite frankly, your body is exposed to an untold number of all different kinds of germs from bacteria, viruses, fungi that might be out there in the world. And most of the time, your body's able to deal with these germs without you hardly knowing about it.

GROSS: Whereas there's no medication that could take care of all of that.

DAVIS: Exactly. So the immune system has to be able to react essentially to germs that haven't even been in the universe before, right? If viruses are changing their nature through mutations - as you're familiar with the idea that there's a different kind of flu coming around every year. And so your body has to be able to deal with viruses and other types of germs that literally haven't ever even existed before. That's how powerful the system really is.

GROSS: Among the many things that I learned from your book is that the immune system's potency changes at different times of the day. What are the changes?

DAVIS: Yes. So that's a really hot area of research. And I have to say that we - you know, this is going to come up I think many times in interviews like this where there are some edges where we don't understand everything. But broadly speaking, your immune system unquestionably changes its power, if you like, during different times of day. And on a very rough level, your immune system might be thought of being a bit more powerful during the night. And part of that is down to the activity of a particular hormone, cortisol. But that's only a first approximation.

So when I say that your immune system is perhaps a bit more powerful at night, in detail, your immune system really is in a slightly different state in day and night because there are some aspects of our immune system that are changing by day and night. And it's only a first approximation to suggest that it's more powerful during the night but certainly changes into a different state by day and by night, which of course leads us to interesting ideas for medicine.

GROSS: Like...

DAVIS: Like, for example, one of the ways we might be able to use this kind of information very specifically would be in vaccination. If vaccines were given at a certain time of day, for example, they may well have a greater benefit. And so we haven't yet got to the point where there's a clear government or health message to say, you know, you should deliver vaccines early in the morning rather than in the afternoon, but we are exploring that type of idea. And my guess is that in the relatively near future, some of that will turn out to be true, that certain kinds of medicines will work better at certain times of day to fit in with the state of your immune system at that time of day.

GROSS: Does this have implications for when our body is most efficient at healing? Like, do we heal more while we're sleeping?

DAVIS: So as a first approximation, that's sort of true. But really, when you dig into the details, there are various bits - the system is such a complex web of all different kinds of cells that interact with each other that when you dig into the details, you'll find that some types of cells in the immune system would be more active at night, and some others might still be more active in the day. Or even more crudely, there'll be different numbers of cells circulating in the blood by day and night.

So there are various nuances to how the immune system changes at different times of day. So roughly speaking, we do have a more powerful healing ability at night. But it's only very approximate to think like that because really there are lots of changes happening to the immune system during the 24-hour cycle, and we don't really understand what all the nuances actually mean yet.

GROSS: In order to talk about the immune system and how things like stress and sleep affect the immune system, we need to talk about cortisol. What is cortisol?

DAVIS: Cortisol is a hormone in your blood that prepares your body for a change in activity. So for example, cortisol levels are generally highest in a person just before you're about to wake up because it's thought that the change in your body needed to wake up requires this hormone to trigger your body to get ready for waking up. So that's where cortisol levels are changing. But cortisol levels also change in any other situation when your body is going to change its activity - for example, during stress, as you prepare for a sort of flight-or-flight response that people would be familiar with.

GROSS: So what does the cortisol do? It heightens your awareness or readiness, or it pumps adrenaline so that you can run away from the thing that is theoretically chasing you like a bear, although really what you're stressed about...

DAVIS: Yes, that's...

GROSS: ...Is a work deadline or a family issue where you're not literally going to be running (laughter).

DAVIS: All of these different - yes, exactly, so all of these different kinds of stress that change your cortisol levels because essentially your body is in this heightened state of activity. As if you're running away from a bear is just the same - although a bit more extreme of course - of you waking up.

And it's just - similarly, even if you're stressed because you've lost your job or because of a long divorce process or any other kind of life situation, all of these types of stresses do lead to changes in your body that are similar, to some extent, in their nature, which includes a change in this level of this hormone, cortisol, to prepare - get your body - your body is in this heightened state of ready for action.

The flight-or-fight response is the thing that people will be really familiar with. And that can happen over a short period of time, as you're - see a bear and you run. But similarly, if you're stressed over a longer-term issue, you still have that type of thing going on in your body but just over a longer period of time.

GROSS: What's the problem if you have cortisol coursing through your body for a long period of time 'cause you're stressed out?

DAVIS: So as part - yes. So as part of your flight-or-fight response, your immediate reaction to seeing some kind of danger - you need to run away - your body shifts its efforts. It gets your body ready to run, for example. And part of that process means that the energy use in your - around your body changes. So you get your muscles ready. Your blood vessels dilate. And you get ready for that running response. And while that's going on, some other parts of the body that perhaps don't seem like they'll be particularly necessary at that moment, like your immune system, do quieten down. And so you don't then have as active an immune system while your cortisol levels are high.

GROSS: Because your body wants to spend more energy running away from the immediate threat, the bear, than it wants to spend at that moment from fighting, like, a new germ. But since you're not really running from the bear and you're stressed out for a long period of time, that's going to be bad for your immune system.

DAVIS: Yes. But I have to say that these are the narratives that we put on the data which are actually quite hard to test. So what you described is exactly the kind of thinking that most scientists would think is likely true. But the exact evidence is really that when a person or an animal is stressed, the immune system does quieten down.

And it could be the type of storyline that we're both talking about, that you don't really need your immune system to fight off germs while you're running away from a bear. But it doesn't have to be that. It could be just that as a consequence of how the body is wired in general, it just so happens that your immune system ends up quietening down while your cortisol levels are high.

It doesn't have to be that there's any real reason for that. It could just be that that's something that happens. And it's actually quite hard to test whether or not, for example, the quietening down of your immune system is just a consequence of how we work or it's really quietening down for a very particular reason.

GROSS: I like that you're acknowledging all the things that science can't really be sure of yet as opposed to just accepting easy narratives that may or may not (laughter) be true. They're convenient.

DAVIS: Yes.

GROSS: They help us explain things, but they haven't really been tested. So thank you for explaining that. It's - it would be more fulfilling for you to tell us for sure what's happening, but (laughter) if we don't really know...

DAVIS: Yes.

GROSS: ...I appreciate you acknowledging that.

DAVIS: Yes. That's actually a really important thing to me, you know, so that when - one of the crucial reasons I wanted to write this book, "The Beautiful Cure," was that as a scientist, everything I want to do is to tell the truth, right? You know, like Leonard Cohen often said in his concerts, I haven't come here to fool you, right?

I don't want to present an easy narrative if we don't have an easy narrative. I want to present the data, the facts, the evidence that we have for things. And then some things are genuinely unclear. And it's not my job to give a definitive or declarative public health message but for people to know what's true, for sure, and what really is a bit fuzzy and for people then to make up their own minds about that, which is a really driving force for me in wanting to spend the time to write a book about the topic.

GROSS: Right now we should take a short break. If you're just joining us, my guest is Daniel Davis. He's an immunologist and author of the new book, "The Beautiful Cure: The Revolution In Immunology And What It Means For Your Health." We'll be right back. This is FRESH AIR.

(SOUNDBITE OF TODD SICKAFOOSE SONG, "TINY RESISTORS")

GROSS: This is FRESH AIR. And if you're just joining us, my guest is immunologist Daniel Davis. He's the author of the new book "The Beautiful Cure: The Revolution In Immunology And What It Means For Your Health." He is a professor of immunology at the University of Manchester in England.

So let's talk about the immune system and cancer. If the immune system fights germs, like bacteria and viruses, what is its role in fighting cancer?

DAVIS: This is an extremely exciting area for immunologists all over the world. We once thought, in fact, that - how could your body fight cancer? What is cancer? Cancer is not usually associated with any particular germ. There are few cases where viruses would cause cancer. But, by and large, cancer is just one of your own body's cells that has gone awry and has started multiplying and dividing out of control and giving you cancer. So it really comes from your own body's cells.

If your immune system is wired up to tackle things that are not part of the body, like germs, viruses, bacteria and fungi, how could it deal with something like cancer? But, in fact, we did discover that the changes that happen in the body's cells to turn a cell cancerous can actually be picked up by the immune system. Now, why it's become really exciting, that realization, is that that opens up the idea that we could perhaps look at ways of boosting the immune response to tackle cancer even better. And as you'll be aware, the Nobel Prize was given just last month to scientists from Japan and America for a wonderful discovery that directly uses that idea with a very specific discovery.

GROSS: What was the discovery?

DAVIS: Right. So essentially, when you're infected with the flu virus, the particular cells in your body that fight that flu virus would multiply in number to fight off the flu. But once that flu virus has been eradicated from the body, you don't need all of those cells in the body. You don't need this heightened state of activity specifically for the flu virus when it's already been eradicated from your body. So the immune system has brakes within it to switch itself off after some time.

So the big discovery that these scientists made were that there were specific brakes to switch off the immune system after some time. And although I just, again, presented it to you as the narrative that got us to understand brakes, they didn't discover it like that. They really discovered it by just following their nose to work out what a particular protein molecule did in the immune system and found out that it switched the immune system off, and it acted as a brake. If there are brakes in the immune system that are coming on when you need a very long-term response in fighting off cancer, that seems like a bad idea.

And so they developed drugs or medicines - antibody molecules, essentially - that block the brakes from working. So they turn off the switching-off signal on the immune system, which allows your immune system to better fight off cancer cells. And so for some patients with some types of cancer, that's been quite revolutionary.

GROSS: Your father has the blood cancer multiple myeloma, and he's been taking the drug thalidomide. Now, in the 1950s, thalidomide was used for - it was often prescribed for pregnant women. Explain why it was prescribed then and what the problem was.

DAVIS: Well, thalidomide was originally given as a sedative to help pregnant women with particular problems in their pregnancy. And it turned out that the drug causes all sorts of problems during pregnancy. And it's a truly tragic situation. And you know, many people have suffered from that. But by chance...

GROSS: Well, separate from - I mean, we should say that the babies were born with deformed limbs or, you know, foreshortened limbs.

DAVIS: Yes.

GROSS: And, you know, it was really kind of tragic. You know, when I was growing up, like, that was the nightmare drug. That was, like, the worst-case-scenario drug for pregnant women. So how is it being used now, in situations like your father's, who has multiple myeloma?

DAVIS: So what happened was that, by accident, essentially, it turned out that although the thalidomide had these horrific consequences - I mean, yes, that huge tragedy in the history of medicine - it was also noted that it did seem to have some kind of anticancer property. And one particular pharmaceutical company essentially took that on. They made a less toxic version of thalidomide. So it's not actually directly thalidomide that my father benefited from but a molecule that is very like that, that's less toxic. And it is now used to successfully treat many cancer patients, including my own father, yes. And so it's...

GROSS: So what does it do? How does it work?

DAVIS: It's not entirely clear how it works. It seems to do many things in the body. It can directly kill cancer cells. But as well as that, it seems to boost a person's own immune system into being able to directly kill cancer cells. And one of the things that, you know - so I don't want to overemphasize my own laboratory's research over others because there are obviously thousands of people working on these things. But in my own lab, we did take that particular drug because it was keeping my father alive, and I wanted to find out more about it, seeing as it wasn't clear how it worked.

And one of the things it does is it allows a particular white blood cell called a natural killer cell, which is a type of white blood cell. There's about a thousand of these cells in every drop of your blood. And they're particularly good at killing cancer cells. And this drug, at least in a dish, allows a cancer cell to be latched onto by natural killer cell. And natural killer cell then kills the cancer cell more easily in the presence of this drug. So it allows the - your own white blood cells to kill cancer cells much more efficiently. And we then watched that process with high-resolution microscopes to look at the molecular processes by which that happens to learn exactly how white blood cells kill cancer cells better in the presence of that drug.

So when a natural killer cell sticks to a cancer cell, it has these packets of toxic molecules withinside (ph) your own natural killer cell that then come out and go on to the cancer cell and kill it. And for those packets of toxic molecules to get out of your white blood cells and kill a cancer cell, it has to pass through a mesh work of other molecules that look like the inside bit of a tennis racket - like the squares of a tennis racket. And you imagine that, through the squares of a tennis racket, these toxic proteins have to come out and then attack a cancer cell. And one of the things that this drug does, which has this shadowy past, this tragic story - one of the things this drug does is it opens up the squares of that tennis racket to be much bigger, which more easily allows your white blood cell to kill a cancer cell.

GROSS: Can you actually see that happening under a microscope in your lab?

DAVIS: Yes. That is exactly what my whole lab is about - that we use microscopes to watch how the immune system works. We want to understand when an immune cell sticks to another cell - we want to watch the process by which the immune cell decides if that other cell is healthy or diseased. And then if the immune cell is sticking to a diseased cell, we want to watch what it does, what happens. And that will help us understand how your immune system works in a very reductionist, molecular way. But that's the right path for giving us new ideas for medicine, I think.

GROSS: Do you think of the things you're seeing under the microscope as being beautiful or ugly? What - if you're looking at disease?

DAVIS: There is a really deep wonder in watching how your immune system works under a microscope. I think it's quite profound. I think that the part of the human body which we understand the best is this - is how your immune system works. It's what happens when you get a cut. It's what happens when your immune system tries to fight cancer. This is the part of our body that we understand with the greatest amount of detail. And watching that play out under a microscope is quite profound. It's quite poetic. I think that we're collectively - the tens of thousands of people that are trying to understand how this system works is a soulful enterprise.

GROSS: My guest is immunologist Daniel Davis, author of the new book "The Beautiful Cure: The Revolution In Immunology And What It Means For Your Health." After a short break, we'll talk about autoimmune diseases, which are caused when the immune system starts attacking healthy tissue. And Ken Tucker will review a box set of "The Complete Recordings" of the late Lefty Frizzell, one of country music's most influential singers. I'm Terry Gross, and this is FRESH AIR.

(SOUNDBITE OF STEVE REICH'S "SECTION II")

GROSS: This is FRESH AIR. I'm Terry Gross. Let's get back to our interview about the latest discoveries about how the immune system works and how that's leading to new medications. My guest is immunologist Daniel Davis, author of the new book "The Beautiful Cure: The Revolution In Immunology And What It Means For Your Health." He's a professor of immunology at the University of Manchester in England where he runs a lab that uses microscopes to learn by watching how immune cells detect and kill diseased cells.

Let's talk about autoimmune diseases. And those are diseases in which something goes wrong with the immune system, and it starts attacking healthy tissue. Describe a little bit more what an autoimmune disease is and give us some examples of them.

DAVIS: OK, so an autoimmune disease is a disease where your immune system has started to attack your body's own healthy cells when, obviously, it shouldn't. And there are many examples of this. Multiple sclerosis, diabetes, rheumatoid arthritis are diseases that, you know, obviously, many people are familiar with. And there are many difficulties in tackling autoimmune disease. For example, by the time a person has come to a physician with the symptoms of an autoimmune disease, it's very often the case that the disease has been running already for some time. And so it's hard to know, for example, what the triggers for the specific bad situation that's happened in a person.

But also, our understanding of how the immune system works has given us some ways in which we can now begin to tackle autoimmune disease.

GROSS: Do we understand why the immune system attacks healthy tissues and organs when someone has an autoimmune disease?

DAVIS: Yes. So the problem is - it's actually an incredibly wonderful process by which that works, that you make an immune system that can react randomly to anything, kill off bits of it that might react to you, and then you're left with stuff that would react to things that could be germs. If you just bear with me a minute, the problem with that is that your body is changing.

For example, there is - during pregnancy, during adolescence, your body is making things that were not part of your body earlier. So how does your immune system deal with that? Food, for example, has not come from a germ, and yet your body doesn't want to react against food, and it's also not part of you. So that means it's very complicated. Your immune system has to have countless regulations, checks and balances, all different cells working together to create a system that can react to anything that's out there that might be dangerous and yet still not react to parts of you.

And so the complexity of it all leads to cracks in how it would work. And sometimes the immune system gets it wrong. Now, the very specific triggers that trigger a problem happening are really difficult to work out. But one idea that's out there is that you would have a germ that really causes a problem, and the germ might have a component of it that looks a little bit like something in you.

So the immune cells would be activated. They would be switched on to kill the germ. And then by mistake, they see a component of your own body that looks a bit like the germ, and they might attack your own body by mistake. That might be one aspect of what happens to trigger an autoimmune disease.

GROSS: There are drugs that are being used and drugs that are in the process of being created and theories that might lead to new drugs for the treatment of autoimmune diseases. Give us an example of a drug in use or in the experimental phase that you think is very promising in treating autoimmune disease.

DAVIS: Well, one of the most successful drugs - in fact, one of the world's most successful drugs, period, never mind just what - is a particular drug called anti-TNF, which actually many of your listeners will probably be using for something like rheumatoid arthritis. And what this drug does is - we've spoken a lot already about the complexity of the immune system, the fact that there are so many different kinds of immune cells, that they somehow have to work together to give a robust response.

So the cells have to interact with each other. And one of the things they do is that they secrete soluble molecules so that one cell will send out a secretion to tell another cell, you know, there's a problem here; we need to be switched on and deal with it. And in fact, one of the scientists, Marc Feldmann, was on holiday in Spain, and he was - you know, he often tells me, in fact, that people need to take more holidays 'cause that's where you get the big ideas.

And he was thinking that if the immune cells are able to egg each other on with these soluble secretions, then perhaps by blocking those secretions - so stopping an immune cell from egging on another immune cell - if we block that, we might be able to stop the immune system from going overboard and reacting in a way that's causing a problem.

And so he, working with a clinician scientist, Tiny Maini, developed a drug called anti-TNF that blocks one of the secretions that come out from an immune cell to egg on another immune cell. He blocked that. And that essentially switches off the immune system. And that prevents an autoimmune disease like rheumatoid arthritis. And it doesn't work for everyone, but it's a hugely successful drug.

GROSS: You write that, you know, older people are more prone to autoimmune diseases. And it seems our immune system goes awry as we age, you say. So what goes wrong with our immune system as we get older?

DAVIS: Yes. That's an incredibly important question, especially as in general the whole of the world's population is increasing in age on average. So it's a really important issue to understand what happens as we age. What we do know is that something in the immune system generally changes as we age. And there are - it's a hot topic. It's another frontier. There are ideas about what specifically might happen.

Remember we spoke about how, you know, when you get a flu virus, for example, you - the cells that fight off that flu virus multiply in number. Then after a time, when you've eradicated the virus, you don't need all those cells around in your body. So your body quietens down, and most of those cells are lost. But you retain some cells that can fight off that flu virus, the memory response that you would have if - sort of stop you getting the same flu again or prevent - allowing your immune system to better fight off the same flu again.

That means that as we age, you would have more and more of your immune system tuned in to fight off all the different history of infections you've previously been exposed to. So if more and more of your immune system is tuned in to fight off the different infections you've had during the history of your life, then perhaps less of your immune system is able to deal with new infections that you haven't been exposed to.

It also means that you'll have more and more of those kinds of cells in your body, the memory - the immune cells responsible for your memory response. And they may give a sort of general low-level of inflammation to your body overall which may allow you to perhaps trigger - you know, lower the threshold, for example, at which an autoimmune disease might develop. But it's a very unclear area of science at the moment but a hugely important topic.

GROSS: So let me reintroduce you here, and then we'll talk some more. If you're just joining us, my guest is Daniel Davis. He is the author of the new book "The Beautiful Cure: The Revolution In Immunology And What It Means For Your Health." And he's an immunologist who's a professor at the University of Manchester in England. We'll be right back. This is FRESH AIR.

(SOUNDBITE OF CUONG VU AND PAT METHENY'S "SEEDS OF DOUBT")

GROSS: This is FRESH AIR. And if you're just joining us, we're talking about how the immune system works and how new medications are being created to use the immune system, to harness the immune system, to help you heal yourself. The book is called "The Beautiful Cure." And Daniel Davis is a professor of immunology at the University of Manchester in England.

Tell us a little bit more about what you're doing in your lab.

DAVIS: My background is actually in physics, so I came to studying the immune system, really, through the idea that we would use microscopes to watch how immune cells work. So we would tag - we'd tag individual proteins inside an immune cell and watch what they do when an immune cell sticks on to another cell. And with that, we start to learn how an immune cell sees diseased cells and then how it - how they would deal with it. Obviously, as a scientist, what's most exciting to me is our most recent discovery, so let me tell you about that.

GROSS: Sure.

DAVIS: So we've been studying how an immune cell sticks on to a cancer cell. And many labs have been watching how it recognizes the cancer cell and how the immune cell then would kill a cancer cell, and lots and lots of scientists have been working on that across the globe.

One of the things that happens when an immune cell sticks to a cancer cell is that after some time, the molecule - the receptor molecules at the surface of your immune cell that see the cancer cell - so you have - you imagine the - a sphere of your immune cell, and you've got these molecules protruding out from the sphere that latch on to the cancer cell. After some time, those molecules protruding out to latch on to the cancer cell, they get chopped off. They get taken off the immune cell.

And people thought, well, that's obviously for the immune cell switching itself off after some time. We've spoken just now about the idea that your immune system has to switch off after some time. And so chopping off these receptors probably leads to dampening down the immune response. So that means maybe we could design medicines that stop these receptors being chopped off.

Now, one of the things that my lab recently discovered was that in fact the complete opposite is true - that an immune cell sticks to a cancer cell. It will kill it. Then it will chop off these receptors that were sticking to the cancer cell so that it could detach itself from that cancer cell. And then that very same immune cell could move on to kill another cancer cell. Then it would kill it, detach from it and then go and kill another cell.

So chopping off these proteins that are sticking to the cancer cell is really important to boost your immune response because it's allowing one immune cell to kill a cancer cell, get off it, go and kill another cell, get off it, go and kill another cell. So this is a process that is helping your immune system. So that is a new avenue for thinking perhaps about a kind of medicine, that we're not just talking about helping the immune cell to kill a cancer cell. What about helping it get off that dead cancer cell and then going to kill another one?

GROSS: So are you cutting that - I forget what it is - off in the lab, or is that something that naturally happens?

DAVIS: So it naturally happens, and people are thinking about preventing that from happening as a way of helping your immune cell fight cancer better. But research would suggest that it's really important that that happens. And in fact, we want to encourage that to happen. A part of the process which seems very important in how your immune cells can efficiently kill off cancer cells is their ability to not just stick to a cancer cell and kill it, but also to then detach from that cancer cell and go and kill another cancer cell.

GROSS: Something that you say in the book - I think you said this at the very end of the book - is that everything about the immune system is counter-intuitive. So that must make it hard for you as a scientist studying how the immune system works.

DAVIS: It makes it hard. But I think also it's part of the reason to study the immune system. You know, we've spoken a lot about how the immune - studying the immune system leads us to new medicines. And that is top priority. Everyone agrees we've got to do that. But also, as I try to suggest in the way we're talking about it, the immune system is unbelievably wonderful.

And the fact that so much of it is counter-intuitive - you know, we have to discover what we are. So it's not self-evident as to how our body is able to fight off an untold number of germs, including those that have never existed in the universe. We have to dig into the details and discover what we are, and some of that is really quite surprising and counter-intuitive.

The concept of an autoimmune disease is utterly counter-intuitive. You know, how could you expect that your body is in some cases going to turn on itself? You know, that is a counter-intuitive idea, which is of course hugely important for medicine.

GROSS: So does that mean you can't go with hunches because - since everything (laughter) - you can't go with your intuition since everything about the immune system is counter-intuitive?

DAVIS: (Laughter) So I likened the study of the immune system - in my book, I likened it to writing a novel. Right? So when you read the finished thing, it makes sense. And you think the novelist or the artist or whoever made that movie you just watched, they probably planned it all out. It was all perfect.

You know, they got the people. They got the best cast. They wrote the script. The story flowed so seamlessly. Oh, it's a masterpiece. And it was such a good idea, and it obviously was going to turn out like that. And of course, you and I know that it doesn't work like that - that whoever wrote that novel, whoever made that movie, whoever wrote that song were killing themselves to do it. You know, like...

GROSS: (Laughter).

DAVIS: I think it's even in one of your earlier interviews that - I think it was Leonard Cohen's son mentioned that Leonard Cohen spent 12 years writing "Hallelujah."

GROSS: Yes.

DAVIS: When you listen to "Hallelujah," you know, it's a masterpiece. Right? Now, I think the beauty of being a scientist is - you know, I'm not pretending that doing science is like writing "Hallelujah." But some aspects of it is the same, that you're digging in, and you don't even know where you're going.

The story ends up being clear and simple, but it wasn't like that in the outset. The stories are created kind of after the fact. And really, when we're in the midst of doing the science, it's just like writing a novel or making a movie, that it's all just messy. And you don't really know where it's going, but eventually it pans out.

GROSS: Well, that reminds me of another sentence that you write in your book, which is, (reading) what keeps scientists going is the faith that nature is coherent and that answers exist.

DAVIS: Yes. I think that's really important. That is what keeps us going, that when all this stuff is happening and nothing quite makes sense, what keeps us going is that there will be an answer - that it must be coherent. There must be some way of explaining the strange thing that I'm seeing down the microscope. And if I dig into it enough, it will become clear. Now one of the important spokes of that, of course, is I've got to choose the right problem because I could dig into anything.

You know, if my computer crashes, is it worth me spending ages trying to work out why it crashed, or should I just turn it off and turn it on again and get it to work again? So it's choosing the things that look like it's worth me digging into or working with my team to dig into. That's the tricky bit about being a scientist 'cause you never quite know from the outset what's going to lead to something important (laughter).

GROSS: Daniel Davis, thank you so much for talking with us.

DAVIS: Well, thank you so much for having me.

GROSS: Daniel Davis is the author of the new book "The Beautiful Cure: The Revolution In Immunology And What It Means For Your Health." After a break, Ken Tucker will review a 20-CD box set by one of the greatest country singers of all time, the late Lefty Frizzell. This is FRESH AIR.

(SOUNDBITE OF PHIL KEAGGY AND HOLT VAUGHN'S "BITTER SUITE") Transcript provided by NPR, Copyright NPR.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.