Immunity

Copyright

Thorsons

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www.harpercollins.co.uk

First published by Thorsons 2020

FIRST EDITION

© Dr Jenna Macciochi 2020

Cover layout design © HarperCollinsPublishers

A catalogue record of this book is available from the British Library

Dr Jenna Macciochi asserts the moral right to be identified as the author of this work

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While the author of this work has made every effort to ensure that the information contained in this book is as accurate and up-to-date as possible at the time of publication, medical and pharmaceutical knowledge is constantly changing and the application of it to particular circumstances depends on many factors. Therefore it is recommended that readers always consult a qualifi ed medical specialist for individual advice. This book should not be used as an alternative to seeking specialist medical advice which should be sought before any action is taken. The author and publishers cannot be held responsible for any errors and omissions that may be found in the text, or any actions that may be taken by a reader as a result of any reliance on the information contained in the text which is taken entirely at the reader’s own risk.

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Source ISBN: 9780008370268

Ebook Edition: March 2020 ISBN: 9780008370275

Version: 2020-03-12

Dedication

To Luca and Isabella who have given me so

much in such a short time.

And to all those who believed in me when

I struggled to believe in myself.

A Brief Note to Healthcare Professionals

In this book I have sought to present some of the current and big ideas in my field, fusing them with my own stories, personal anecdotes and my passion for this subject. My aim was also to convey a sense of wonderment for this silent system and the vast and complex science it encompasses. I am acutely aware that this is not – and could never be – an exhaustive text on the immune system. In my attempt to keep the narrative and scientific ideas as clear as possible for the general reader, I could not cover all the topics I wanted to or discuss them in the depth they may warrant. And rather than present a complete textbook-level description, I have deliberately chosen to focus on the broader contemporary issues – to bring an awareness to how modern lifestyles and our rapidly changing environment interact with and shape our immunity and, ergo, our health. In my quest to be evidence-based I have dived into the scientific literature, consulted with colleagues and reached out to other experts along the way, combining this information with case studies and alternative health literature to give a balanced and holistic overview. In some cases the only ‘evidence’ available is weak or at least not the most rigorous, so I have made efforts to state this where appropriate. Ultimately, any one book can only tell part of a story and this, I hope, is just part one.

Contents

1  Cover

2  Title Page

3  Copyright

4  Dedication

5  A Brief Note to Healthcare Professionals

6  Contents

7  CHAPTER 1: How to Be Well in a Modern World

8  CHAPTER 2: Living for Longevity

9  CHAPTER 3: Have Your ‘Old Friends’ Got Your Back?

10  CHAPTER 4: Sleep, Seasonality and Circadian Rhythms

11  CHAPTER 5: Mental Health Matters

12  CHAPTER 6: Intelligent Movement for Modern Life

13  CHAPTER 7: Immunity-nourishing Nutrition

14  A Final Word

15  References

16  Further Reading and Resources

17  Acknowledgements

18  Index of Searchable Terms

19  About the Publisher

LandmarksCoverFrontmatterStart of ContentBackmatter

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CHAPTER 1

How to Be Well in a Modern World

‘There is no permanent ideal of disease resistance, merely the shifting sands of impermanent obsolescence.’

MATT RIDLEY, author

Described by the US National Library of Medicine as ‘the most complex system that the body has’, our immune system is a vast constellation of cells and molecules spanning every nook and cranny of our bodies.

WHAT’S IMMUNITY AND WHY SHOULD YOU CARE?

‘Immunity’, from the Latin immunis meaning ‘exempt’, refers to the art and science of the human immune system – the various biological defence systems that keep us well. The immune system is a silent wonder. While we are very aware of our hearts beating and the breaths we take, we are much less aware of our immune system and the many jobs it performs to keep us well. This mighty system protects our health by resisting uninvited infections, maintaining order and balance in our bodies, and healing wounds. It is our foundation to wellbeing.

Immunology, the extraordinarily rich, yet complex study of the immune system, has changed the face of modern medicine over the last 30 years. There has never been a more fascinating time to delve into immunology and harness its power to improve your health. And that is what this book will do for you. Based on cutting-edge, evidence-based scientific research, this book takes you on an empowering journey through the latest astonishing discoveries in immunology. You will get to know the immune system inside out and come to an intimate understanding of how it works.

It is not often that one body system touches so many aspects of human biology in both sickness and health. Although it is seemingly esoteric and beyond comprehension at first blush, the immune system is the epitome of versatility and simplicity of purpose.

When it comes to maintaining good health, the immune system is our most precious asset, yet we rarely appreciate our essential defences until something goes wrong. We thank our immune system when we catch a cold and scramble for vitamin C supplements in the winter months. But what about all the other wonders it works? If it only existed for the first few weeks of chilly weather every year, we’d all be in serious trouble. Most of the time our immune system is working away in the background and we don’t even notice it. Deeply entwined with every aspect of our physical and mental health, it lays the foundations of our health and longevity.

Immunity is a sophisticated system, with astonishing complexity. But there is a lot that can go wrong, from autoimmune diseases and allergies, to mental-health problems and metabolic issues – even cancer. We have an obsession with looking healthy and being well, and yet we are sicker and unhappier than ever before. That’s because our delicately balanced immunity is easily compromised by our ever-accelerating pace of life, with its relentless stress, pollution, overconsuming and under-moving. What modern life deems ‘healthy’ may not actually be so. Today, we’re more likely to die from a lifestyle-related disease than any other cause, and many of these would be preventable if we took better care of our health.

On our journey through modern immunology, you’ll discover why the immune system is your sixth sense, connecting your health to your environment, feelings and emotions; why some people rarely get sick; what to do if you have a chronic illness; and what it really means to ‘boost’ your immunity.

My endless wonder at this vast and elegant system, integral to our wellbeing, has been the driving force behind both my career and personal life. From an early age I was intrigued by the human body, health and disease. My mum, a trained cook, strongly believed that health was in our own hands and taught me the old-fashioned cookery basics that have become a vital tool in my modern-day mum–life toolbox. She was the original purveyor of old wives’ tales. Yet there was a wealth of untapped wisdom in her words that left me with a lingering curiosity, shaping my path as I embarked on my scientific career.

As I’ve discovered more about the immune system, I’ve found myself changing how I live in response to what I’ve learned. I’m driven to question what modern life tells us is healthy, yet makes our immunity go awry. Every day I find myself hunting for clues, researching the evolution of the immune system and thinking about the traditional ways of life that have shaped our health. Have we thrown the baby out with the bathwater by swapping old ways for new and shiny modern ones? This is a question I keep coming back to, and one which I’ll answer in the chapters that follow, while also exploring how we can reclaim our innate knowledge of immunity through traditional rituals, supported by science. Keep in mind as you move through the chapters that the immune system is a bit like a wiggly moving octopus. Its undulating nature makes it difficult to cover it in a linear, page-by-page fashion. And one of its slippery charms is that the answer to many questions about it begin with ‘It depends’ or ‘It’s complicated.’ Understanding the secrets of how to be well requires a balance between openness to new ideas (no matter how counterintuitive they may seem) and ruthless scrutiny of all concepts both old and new.

Despite its immense power, we often hear calls to ‘boost’ our immune system through food, exercise or a wellbeing practice. Although there remains much to learn about its interconnectedness and intricacies, to function well the whole system requires balance, not boosting. Read on as I explain what this means for your health.

INFECTION PROTECTION

The immune system is all that stands between us and the hordes of microbes (also known as germs, these are microscopic organisms including bacteria, fungi and viruses too small to be seen by the naked eye) that threaten us constantly. Hippocrates (460–377 BC) was the first to find a scientific explanation for disease. His was the theory of the four humours (yellow bile, black bile, phlegm and blood) in the body – the idea that these were in balance in healthy beings, but out of balance in a sick person. Sickness, he claimed, was the result of an excess of one of the humours, caused by miasma (poisonous vapours or mist filled with particles from decomposed matter) or miasmata (vapours coming from decomposing organic material such as waste, manure or dead bodies). This theory may sound strange to us now but reflects the limited tools and technologies available at the time. Without a way to ‘see’ germs, scientists didn’t have much to go on. In the mid-19th century, as equipment for poking and probing evolved, ‘germ theory’ – devised by Louis Pasteur (the father of immunology) and his contemporaries – emerged and soon replaced the four humours in public consciousness. Germ theory is how most of us think of immunity: germs are bad, and immunity’s white blood cells are our guardian protectors. But of course, nothing with health and immunity is ever that simple.

Immunity is hard-wired to detect and differentiate between what is us (self) and what is foreign (non-self), such as a germ. This makes it easy for our immune system to decide what to attack: non-self potentially dangerous germs that need eliminating, (normally) sparing our own precious tissues.

The immune system has had a complicated, you might even say fraught relationship with germs over the years. For centuries we have drawn a causal conclusion that microscopic germs cause illness – and for good reason. Devastating outbreaks, infection epidemics and perplexing illnesses have all been caused by the veritable smorgasbord of micro-organisms that we share this planet with. Over the last decades our fear of them has been realised, with devastating reports of swine flu, Zika, Ebola and many others – each outbreak prompting new concerns about infection protection. But from birth to death we are silently bombarded, minute by minute, with an untold number of potential infectious threats. Whether we get sick or not is decided by the integrity of our immune system. Most of the time, our immunity deals with these germs without us even knowing about it. That’s how powerful the system really is. There are no medications that can protect us in our infectious world quite like our immune system.

THE IMMUNE SYSTEM: A REALLY, REALLY, REALLY BRIEF EXPLAINER

Though vastly complicated and mind-bogglingly confusing, as any of my immunology students will tell you, let’s try and keep it real simple.

The immune system is not, in fact, one thing, and it’s not in one place. Rather, the immune system is a whole galaxy of cells known as white blood cells (leukocytes, to give them their proper name). Immunity also includes lymphatic organs (such as lymph nodes, bone marrow and spleen), molecules (cytokines) and their collective array of biological functions. The bone marrow is your immune-cell factory where new immune cells are born from stem cells – a blank-canvas cell with the capacity to evolve into any one of your numerous immune-cell types. Despite their name, white blood cells are not just found in your blood, but in strategic locations all over your body. Every single one of them brings its own particular skill set, featuring an array of receptors and molecules capable of inducing the many different flavours of an immune response.

Border Control

A good way to start understanding the immune system is to liken it to a castle – a fortress with many layers of defence, all working as a close-knit team. Your body’s borders act as the first line of immune defence: skin and the mucus membranes that line your natural openings – such as your mouth, nose and digestive tract – are part of your immunity, making and releasing substances that create a hostile environment for the invaders or attacking and destroying them directly. These physical barriers are as delicate as they are protective, with inherent vulnerabilities, and over the millennia just about every germ that wants to get in has evolved ways to help it do so. In response, our immunity – or castle – has devised a sophisticated system, choosing the best and discarding the least useful bits of our elegant defence mechanisms, so that every barrier surface has its own unique set of immune defences designed for that location.

Priority Setting: Full-Frontal Innate Immunity

Put simply, the cells and molecules of the immune system comprise two parts: innate and adaptive (which we will come to soon). Together, they are your body’s safeguard. Innate response is what you notice when you first get sick (inflammation is an example of an innate response). It attacks with a vigorous, feet-first approach. What our innate immune response lacks in specificity, it makes up for in speed. The starting line-up features the innate cells. Like scattered ‘listening posts’, these are diverse and everywhere in our body. They act as sensors, hard-wired to detect anything out of the ordinary, eating germs and debris, calling for backup. Legions of these innate immune foot soldiers rush to assess a problem, attack it with potent killers to defend (and potentially harm) our bodies, causing significant collateral damage to our own tissues. Our immune system’s beautiful destructive dance, with its characteristic heat, swelling, redness and pain, looks like the scene of a microscopic multi-car crash. As this happens, you may spot those familiar signs – a stuffy nose, sore throat, tummy ache, fever, fatigue or headache – and then go on to experience familiar symptoms such as increased mucus, pus and a cough.

Now, while inflammation is a vital immune response and fundamental to our health, it is, by design, only supposed to be an acute, short-term assault. This is because it is as damaging to our own tissues as it is to invaders. Triggered incongruously, it can cause problems long after the initial danger is gone. As we’ll explore, inflammation is core to our modern-day health niggles, existing on a continuum: from mild symptoms such as weight gain and fatigue at one end, to heart disease, depression and autoimmune conditions at the other.

The Path to Resolution

When we are sick, the body needs inflammation. But if this response continues for too long, it becomes counterproductive. The imprecise inflammatory defences discharged by innate cells can wreak havoc on our delicate tissues and even on entire organs. The immune system needs at some point to reduce the inflammation and has therefore acquired the tools to regulate it. So how does inflammation lessen? Let’s explore.

Acute inflammation and all its associated chemical weaponry also upregulates many anti-inflammatory mechanisms to temper the fire. Special pro-resolving mediators (signalling molecules) are naturally produced in the body during the process of inflammation. And they, ultimately, close the loop on the whole process. Rather than turning the immune system off (and risking infection), resolution works in collaboration with inflammation, letting it do its job before gently inviting back the status quo.

Common over-the-counter anti-inflammatories such as ibuprofen or acetaminophen (paracetamol) block important pro-resolving signals, inhibiting the way our bodies naturally resolve inflammation. This is why they are not recommended as a long-term treatment. Aspirin, on the other hand, does not block but gently attenuates, while also stimulating resolution – which is why it is sometimes recommended at a low dose for certain inflammatory conditions. Resolution of inflammation might not seem like such a big deal, but it’s paradigm-shifting, with vast potential to aid our modern-day health crisis, controlling chronic inflammatory disorders and promoting wound healing. We can support the resolution of inflammation in other ways too, which, as you will read, may be our best chance during future health challenges.

Slow and Specific Wins the Race

Innate immunity is pretty darned good at quickly detecting and eliminating potentially harmful germs, sensing and repairing damage, and quietly removing old or malfunctioning cells. But although it provides immediate protection against intruders, it is incomplete at best. When stressed to the limit, it has to call on its big brother: adaptive immunity.

If innate immunity is an initial shotgun blast at all the bad guys, adaptive immunity is a targeted missile. It’s a second-line defence that takes a while to kick in – some five to seven days. Unlike innate immunity, which can involve a veritable horde of white blood cells, adaptive immunity is controlled by the lymphocytes. There are two categories of lymphocytes, known as B lymphocytes and T lymphocytes. T lymphocytes are the master controllers, sent out into the body, controlling the levers of many other arms of immunity; B lymphocytes are our special reconnaissance unit – the antibody producers.

Each of us has a unique repertoire of T and B lymphocytes, adding a layer of individual exclusivity to our immunity and, consequently, our health. An immune system that doesn’t produce a huge variety of unique T and B lymphocytes will probably miss or ‘not see’ certain germs or viruses, and these could go on, unchallenged, to cause disease. This happens during ageing, for example as we will explore in the next chapter. Adaptive immunity is a remarkably effective process. But much like the innate inflammation response, when it is improperly triggered, it’s equally bad for our health, as we’ll see.

Blurring the Lines

To fight off infection and disease, the innate and adaptive parts of our immune system collaborate to detect and destroy anything recognised as foreign or dangerous in the body. We first need to co-opt the innate immune system to capture germs and present them via some oh-so-important compatibility molecules (more on these in a bit) to T lymphocytes waiting in anticipation. The innate immune system is an ingenious doorbell that awakens the adaptive immune response with germs in a format they can recognise.

T lymphocytes then swing into action, cloning themselves into huge armies to maximise their fighting power and differentiate into specialised subsets – driving, fine-tuning and sometimes regulating other immune cells – to maximise the chance that intruders are eliminated at minimal cost. Lymph nodes bring B and T lymphocytes together with innate cells at the right place and time. This is why your lymph nodes become swollen when you’ve got a cold coming on.

Collectively, the immune system is, in fact, a model of versatility rather than rigid divisions. Feel those swollen lymph nodes next time you have a sore throat and congratulate yourself on successfully linking the innate and adaptive immune systems.

How Is Your Memory?

Innate immunity is vital for life, but it only has a short-term memory. So instead of mounting a faster and more effective response upon encountering a known trespasser, it starts sluggishly from scratch each time. The adaptive immune system, however, is like a library of ‘memory’ cells. Information on every virus, bacteria or fungi that ever invaded your body and was defeated by your immunity is archived by this immune system, identifying them by their molecular shape. This is called immunological memory. And it almost never forgets!

Memory cells do not actively fight the current infection. They patrol the body in case of future infection with the same germ, so when we face that same disease-causing germ, this retained memory means we know how to defeat it – often even before we’ve experienced any symptoms. This explains why you only catch certain diseases once, such as (in most cases) chickenpox, despite repeated exposure. More cunning viruses, however, like influenza and rhinovirus (the cause of the common cold), have developed sneaky ways to evade our immunological memory by continually changing their molecular information.

Natural Born Killers

Natural killer (NK) cells are, as their name suggests, killing machines. Unlike T and B cells, these are not produced in response to a specific antigen (toxin). Instead, they recognise changes in our own cells. These cells are crucial to our health, rapidly responding to kill our own cells when they get infected with a virus.