Instant Genius - How to keep your immune system healthy

Episode Date: April 14, 2024

We often hear about the importance of our immune system, but how can we maintain it and keep it healthy? The answer is easier than you might think. We spoke to Bobby Cherayil, the author of the new book The Logic Of Immunity, deciphering an enigma to learn more about the importance of a healthy immune system. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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and this is the Instant Genius podcast, a bite-sized masterclass from the BBC Science Focus magazine. We are often told about the importance of our immune system. It defends the body from infections, and it protects ourselves. But how do we create a healthy immune system, and why do some people suffer from autoimmune diseases? We spoke to Bobby Shirell, an associate professor of pediatric.

at the Harvard Medical School, an author of the new book, The Logic of Immunity. Deciphering an enigma, he dispels immunity myths and explains what is behind a healthy immune system. I think it's important to go right back to basics here. So when we talk about the immune system, what is it exactly that we're referring to? So the immune system is the collection of cells and molecules

that have evolved the purpose of the purpose, of protecting our bodies from the microorganisms that surround us. And what would you say is, I guess, the role of this combined feature, the immune system as a whole? The primary role is really defensive in nature, and that is to make sure that the microorganisms that we are always surrounded by on every surface that we touch in the air that we breathe, those microorganisms don't have a chance to invade deeply into our tissues and potentially cause damage. And can you give some examples of those? What is it the way are being protected from? The way in which the immune system works is to have several layers of defensive mechanisms.

So the first component is what we refer to as the innate immune system. And that includes the mechanical barriers that are provided by our skin and by the linings of our gastrointestinal and respiratory tracts and other surfaces, and the immune cells that lie immediately adjacent to those surfaces that are in contact with the exterior world. So the mechanical barrier acts to keep separation between the microbial world and the cells that form our body. If that mechanical barrier happens to be breached, then there are the immune cells that lie immediately adjacent to the epithelium that are able to then mount a defensive response. Usually that is also accompanied by the recruitment or calling in of cells, immune cells, that are circulating in our blood at all times.

And these cells act as a sort of roving patrol, a backer. that can be called in to sites where a breach has occurred. While all this is going on, messages are sent in the form of cells that travel to our lymphoid organs, which is where our lymphocytes, the B cells and T cells, that form the second layer of our defense reside. And those messages conveyed by the cells traveling from the periphery to the lymphoid organs indicate the lymphocytes that there is a potentially dangerous situation in the periphery and that they must mount the appropriate response.

And those responses include the production of antibodies, as well as the deployment of T cells that help to eliminate the threat that has occurred at the periphery. And when we talk about an immune system, we talk about it with this idea of having a healthy immune system and a healthy system to fight off illnesses and problems. How do we go about creating a healthy immune system in ourselves? Well, the immune system is very well able to take care of itself under most circumstances,

and we don't need to do anything active to enhance its function, as long as we lead a reasonably healthy lifestyle, meaning consumption of a healthy diet, getting appropriate amounts of sleep and exercise, avoiding potentially harmful behaviors such as smoking, excessive use of alcohol and other stimulants, then the immune system is able to function optimally and protect us from microbial threats. So often there is, I guess, products that emphasize an idea of improving your immune system or to certain vitamins or products that give this argument that they will boost it, is their truth to that, or is that

something that maybe is a bit more far-fetched? No, I don't think there is much validity to those claims. And the various products that you're referring to that are advertised as boosting your immune system really do not have that ability if they are rigorously tested. So I think your listeners should not give too much credence to such claims. And as I said, the important thing is to lead a healthy lifestyle. And as long as you do that in terms of eating the appropriate foods and getting the appropriate amounts of sleep and exercise, your immune system is able to take care of itself and function in the way that it should. And obviously, you can sleep well, you can eat well, you can take care of a lot of these factors.

But for a lot of people, things like stress and burnout can become quite big parts of their lives and can be quite hard to battle. I assume that's an opposing factor which can limit your immune system. Yes, certainly adverse behaviors or adverse experiences can have effects on immune function. They generally have to be in a fairly extreme state in order for that to happen. So I think most of us would probably not have such adverse effects, fortunately, but they can. So if you have a very malnourish diet or you are very deficient, in the consumption of vitamins or essential minerals that can have adverse effects on immune function. But usually they have to be in a fairly extreme state of deficiency.

And for those people that are, I guess, in an extreme state, you know, the very rare groups, do they end up in a position where they're more comparable to, I guess, allergies and daily issues from the world around them? Well, I think you have to be careful in terms of what you mean by a compromise state. So we typically think of immune compromise as being a state of impaired function or deficient function, and that would make you generally more susceptible to infectious disease rather than allergies. On the other hand, there can be circumstances where your immune function may be abnormal rather than being deficient or impaired. It may be skewed slightly in a way that might make you predisposed to developing allergies or autoimmune conditions.

So I think you have to be careful in distinguishing immunodeficient states or immunocompromised states from states of abnormal immune function that might make you more predisposed to developing allergies or other immune-mated disorders. And do we know why the immune system develops differently for different people? Is there a reason that some people can face these autoimmune issues? Yeah, it's a very interesting question, and it's something that I've been interested in for much of my professional career. And there are many factors that contribute to a predisposition to developing the kind of problems that you're referring to. The first is genetic variation. So that accounts for about 40 to 50% of the variability between individuals in terms of immune function.

So the genes that control the immune system are amongst the most various. between individuals amongst all the other genes that are involved in the functioning of our body. And so the genes that control your immune system, for instance, are probably a little different from the genes that control my immune system. And those differences can contribute to the way in which the immune system responds to a particular threat or stimulus. So that's one factor. Then beyond that, there are several non-genetic factors that also contribute to the variability between individuals and that might predispose one individual to developing an allergy or an autoimmune condition. This includes lifestyle factors, the kind of diet that you consume, the location where you reside, the kind of pollutants and other environmental factors that you are exposed to, to whether you have a pet in the house or not,

all these can influence the functioning of your immune system either directly by changing the function of the cells that make up your immune system or by altering the composition of the resonant microbial community that is present on our skin and our mucosal surfaces, which is known as the microbiota. And so, for instance, diet can have a significant effect on the composition of your microbiota, and that in turn can influence your immune system

because research conducted over the last 20 years or so has shown that the microbiota has a profound effect on the functioning of the immune system. So the microbiota can interact with the cells of your immune system in various ways and alter the function of the cells of your immune system. And those alterations can have an effect on the way that your immune system as a whole is able to respond to a stimulus or a particular threat. So in addition, there are demographic factors such as your age and your sex that can influence the way that your immune system functions. And then finally, your previous immunological experience, the history of the microbial encounters or encounters with other types of stimuli, those encounters have a

either relatively short-term or long-term effects on your immune system. In a way, they sort of imprint the immune system as a result of that experience. And so that previous experience can also influence the way your immune system responds to a particular stimulus or threat. So there are these multiple factors that vary between individuals. your genes, the various demographic factors, your microbiota composition, and your previous immunological experience. And so it is the combined effect of these influences that might predispose one individual to developing an allergy on autoimmune condition versus another individual.

And obviously you can't change your demographic status. You can't fix your genetics in that sense. but for people that have found themselves in that position, is there things they can do to improve their autoimmune issues or something similar? Yeah, so one of the things that can be manipulated or changed is the composition of your microbiota. And given the importance of the microbiota in the education and functioning of the immune system, there are various things that we can try to do to make sure that our microbiota is healthy and has a composition that facilitates and allows normal immune function. The most important thing is to avoid the unnecessary use of antibiotics,

because each time you have to take antibiotics, that inevitably alters the composition of your microbiota. And those effects can be quite long-lasting. Even if you take a course of antibiotics that lasts only a few days, the microbiota changes can persist for several weeks afterwards. and those changes can then secondarily impinge on your immune function. So avoid unnecessary antibiotics. The second, of course, is your diet.

So extremes of diet, as I mentioned earlier, can have effects on the composition of your microbiota. So a very high-fat diet causes changes in the microbiota, and those changes can have effects on the functioning of your immune system. and that function can be a little abnormal. So very high fat diets have been associated both in animal studies and in human studies with a slightly hyper-activated state of the immune system, which can be detrimental under certain circumstances.

I just want to go back a little bit because we were saying about different factors that are involved, and we're talking about age. I wonder how your age does impact your immune system in a long period of time, obviously when you're young, you're more likely to have a healthy immune system. Once you get into your old age, how does that impact your general immune system? Yeah, very good question. So there are deviations from the norm at both extremes of age. In very young children, so during the first year of life, the immune system is still developing.

It's in flux, and certain aspects of immune function are not fully developed. so you can have selective impairments in certain aspects of immunity. Similarly, at the other extreme, when you're, say, 65, 70 years and older, you also develop certain impairments of immune function. And that has to do with the fact that as you age, you accumulate damage to your DNA. You accumulate cells that have reached the end of their normal lifespan. and those changes, those age-dependent changes, can also affect the functioning of the immune system. So over the age of 65 or 70, the composition of the cells of your immune system changes.

There is an increase in the proportion of one particular subset of immune cells that tend to be rather inflammatory in nature. So one of the characteristics of the aging immune system is a tendency to be, more inflammatory, and that can affect the susceptibility to certain types of diseases. There is also a tendency to produce antibodies that are directed against your own self-components, which can be damaging. And because the combined effects of these age-dependent alterations in immune function, again, there can be impairments in the ability to mount a normal response to infection, for instance, so that you become more susceptible to certain types of microbial pathogens. As I'm sure you're very well aware,

there's this big push of, you know, anti-aging or ways to slow your aging, fight your aging, whatever version of it people like to talk about. If there's someone who is worried about the way that their immune system will change as they age, is that things they can do to prepare for that stage. Again, I can only emphasize the importance of maintaining a healthy lifestyle for as long as you are able. And that includes the consumption of a balanced diet, getting as much exercise as you are able to,

commensurate with your age, and avoiding behaviors that could be potentially detrimental, such as smoking, excessive drinking, and so on. Other than that, there are no specific supplements or other types of interventions that I can recommend to combat the effects of aging on the immune system. Supplements are a definite no is what I've learned. I would not take any supplement that I advertise, no. I would not.

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and unforgettable listening experiences at home. Try it for yourself at a focal powered by name boutique. Visit focal powered by name.com for more information. Obviously, the field of immunology is constantly evolving and changing and there's always new things that are going to be happening. Are there any exciting areas of research in the area that you think are really important that are going on right now? Yeah, I think there are two really interesting and important areas of immunology that are developing.

The first has to do with the treatment of tumors. So the immune system plays an important role in monitoring for the emergence of malignant cells and then for dealing with them. And with the increasing realization of the importance of the immune system in this anti-tumor function, people have developed ways to manipulate the immune system or to harness certain function of the immune system in order to treat tumors. And there have been some really dramatic successes in this area. So you may have heard of a particular treatment strategy known as immune checkpoint therapy. This is a therapy that has emerged over the last 10 years or so, and that

was awarded the Nobel Prize in 2018. And this has to do with an understanding of certain molecules of the immune system that prevent the immune cells from dealing with malignant cells or tumors. And these investigators have found ways to counteract the effects of these molecules so that the immune system can then be restored to its normal function and clear the tumor that has emerged. There are also ways in which immune cells can be deliberately engineered using genetic techniques to be targeted against the tumor and to kill the tumor in that fashion. So there are other strategies that make use of properties of the immune system that are being harnessed for the treatment of tumors. And I think over the coming years, we will hear more

about these developments. And hopefully they will lead to greater successes in being able to treat cancers and tumors. So that's one big area that I think is very, very exciting. The other is the study of the interactions between the nervous system and the immune system. Again, this is an area that has emerged over the last five, or at least has been getting greater attention over the last five to ten years. And there are many, many interesting observations regarding how immune cells and nerve cells talk to each other. And that can have implications. for treating immune-mediated disorders, and perhaps even for the treatment of diseases and disorders that have their origins in abnormalities of the nervous system. So I think this is also an area

where we will see more and more interesting results and perhaps treatments emerge over the next five to ten years. So we've covered a lot of different factors of the immune system. I'm curious what you think for, I guess, the average person, what are the things that they should be thinking about with their immune system or that they should know about things to focus on in this very wide topic? Yeah. So I don't think you need to think about the immune system on a daily basis. As I said, the immune system is evolved over millennia and it's, you know, it's a very sophisticated self-regulating system and you don't have to worry about it for the most part. It will take care of itself. It will function normally as long as you do not abuse it in the ways that we've discussed earlier.

So as I said, again, I can only repeat that, you know, leading a healthy lifestyle is the best way to make sure that your immune system functions in the way that it should. So live a healthy lifestyle and everything else is fine. Yep. Live a healthy lifestyle. Make sure you get a good diet, balanced with all the right micronutrients. Avoid antibiotics except when absolutely necessary. get enough sleep, get enough exercise, and be happy.

Thank you for listening to this episode of Instant Genius. That was Bobby Shirel on Immunity. The Instant Genius podcast is brought to you by the team behind BBC Science Focus magazine, which you can find on sale now in supermarkets and news agents, as well as on your preferred app store. Alternatively, you can come and find us online at sciencefocus.com. This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal.

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