How the Immune System Works

Citation

Sompayrac, L. M. (2022). How the Immune System Works (7th ed.). Wiley-Blackwell.

Chapter Summary

The book is short, about 175 pages, and is written as seventeen "lectures" in a direct, conversational voice. In "How to Use This Book" the author says plainly that it is neither a comprehensive text nor an exam-review tool but an overview meant to show how the immune system fits together, without the jargon and detail of the large textbooks. Each lecture opens with a "Heads up!" box outlining its argument, and the publisher describes an expanding summary figure at the end of each lecture that builds up a picture of how the parts of the system interact. The author advises reading Lectures 1–10 quickly as a group, then returning to them more slowly; Lectures 11–17 apply what has been learned to real examples.

Lecture 1: An Overview

A "turbo" tour of the whole system, framed by an analogy with a football team: watching one player makes no sense without seeing the whole play. The lecture introduces physical barriers, the innate system and the adaptive system, compares innate and adaptive immunity with the image of an off-the-shelf shoe shop and a custom shoemaker, and ends by arguing that the innate system acts as the "coach", assessing danger and telling the adaptive system what to do.

Lecture 2: The Innate Immune System

The hard-wired defence that has evolved to recognize pathogens that commonly infect humans and to respond quickly against everyday invaders.

Lecture 3: B Cells and Antibodies

B cells and the antibodies they make, as part of the adaptive system that protects against both common and rare pathogens.

Lectures 4–6: The Magic of Antigen Presentation; T Cell Activation; T Cells at Work

The T cell story in three steps. T cells recognize only antigens properly presented by specialized antigen-presenting cells; they must be activated before they act, which helps ensure that only useful weapons are mobilized; and once activated, helper T cells orchestrate the response while killer T cells destroy infected cells.

Lecture 7: Secondary Lymphoid Organs and Lymphocyte Trafficking

How B and T cells circulate through the secondary lymphoid organs in search of invaders, and how, once activated there, they are dispatched to the parts of the body where they are needed.

Lectures 8–10: Restraining the Immune System; Self Tolerance and MHC Restriction; Immunological Memory

How the system is kept in check and reset after an infection; how T cells are tested to focus on properly presented antigen and how self-reactive lymphocytes are screened out; and how memory differs between the innate system, which "remembers" long-standing human pathogens, and memory B and T cells, which respond faster to a repeat attack.

Lecture 11: The Intestinal Immune System

How the immune system deals with the trillions of microbes living in the intestines, which the author calls a hot topic in the field.

Lectures 12–13: The Immune System Gone Wrong; Immunodeficiency

What happens when the system errs, with allergies and autoimmunity as the examples, and when it is too weak, with HIV-1 infection as the main case.

Lectures 14–16: Vaccines; Cancer and the Immune System; Immunotherapy

Vaccines as a safe imitation of infection that primes the immune system; the built-in conflict between avoiding attacks on self and destroying cancer cells; and the medical use of the immune system's own weapons.

Lecture 17: COVID-19 and the Immune System

New in this edition: the pandemic as a natural laboratory for the immune response to respiratory viruses, and the advances in vaccine design, including the mRNA platform, that came out of the COVID-19 vaccine programme.

Key Concepts

Lectures 1–3: The Two Teams

• Innate versus adaptive immunity: a fast, ready-made defence against common pathogens, and a slower, custom-made response built by clonal selection.
• Innate system as decision-maker: the innate system judges the danger and gives the adaptive system its "game plan".
• B cells and antibodies: the adaptive arm that produces antibodies against a vast range of targets.

Lectures 4–10: How the Adaptive Response Is Run

• Antigen presentation: the requirement that T cells see antigen displayed by specialized presenting cells.
• T cell activation: the safeguard that only useful T cells are mobilized.
• Lymphocyte trafficking: the circulation of B and T cells through secondary lymphoid organs and their dispatch to sites of infection.
• Self tolerance and MHC restriction: the screening that removes self-reactive lymphocytes and keeps T cells focused on presented antigen.
• Immunological memory: faster and more effective responses to a pathogen met before.

Lectures 11–17: The System in Health and Disease

• Immunopathology: allergy and autoimmunity as the system "gone wrong", and immunodeficiency as the system too weak.
• Vaccines and immunotherapy: deliberate use of the immune response to prevent and treat disease.

Critical Analysis

Strengths

• The big picture first. The author wrote the book because thick textbooks bury the overall view in detail. The first lecture surveys the entire system before any single component is examined, and the summary figure that grows lecture by lecture keeps that view in front of the reader.
• Memorable explanations. Lecture 1 shows the method: sports and shopping analogies make the division of labour between innate and adaptive immunity easy to grasp, and the "Heads up!" boxes and highlighted key passages and terms make each lecture quick to review.
• Honest about open questions. The author points out at the end of most lectures some "known unknowns", questions immunologists cannot yet answer, which counters the impression that the subject is closed.
• Current applications. The later lectures cover the intestinal immune system, immunotherapy and COVID-19, and the description notes updated material on vaccines, memory and cancer.

Limitations

• Deliberately incomplete. By the author's own account the book is not a comprehensive text or an exam-review tool. It is an introduction to the concepts, so the molecular and clinical detail required in a medical immunology course must come from elsewhere.
• No exercises. The lecture format offers outlines, summary figures and highlighted terms, but the contents list no question sets or answers, and Lecture 1 closes with an epilogue rather than exercises; self-testing has to come from another source.
• Informal tone. The conversational style and analogies suit a first pass, but students will still need to learn the formal terminology that the book keeps to a minimum; the glossary and acronym list at the back help with this.

Where It Fits in the Course

This is the place to start immunology in this course. Read it before Abbas, Lichtman and Pillai's Basic Immunology, a short but full textbook that covers innate and adaptive immunity, antigen recognition, lymphocyte activation and effector mechanisms, then applies them to hypersensitivity, autoimmunity, immunodeficiency, transplantation and tumour immunity. The two books follow broadly the same path, so each lecture can be read just before the matching part of Abbas.

For the infection side of the course, Gillespie and Bamford's Medical Microbiology and Infection at a Glance gives a concise illustrated survey of pathogens and infectious disease, and Mims' Medical Microbiology and Immunology joins microbiology and immunology in a system-by-system textbook. Mims' Pathogenesis of Infectious Disease and Jawetz, Melnick & Adelberg's Medical Microbiology are later and more detailed reading. Sompayrac's lectures on vaccines, immunodeficiency and COVID-19 make a natural bridge to those books.

How to Use This Book

The publisher addresses the book to medical, bioscience, veterinary and nursing students, to researchers wanting a quick refresher, and to general readers; basic cell biology is the only real prerequisite.

Follow the author's own plan. First read Lectures 1–10 straight through, in a couple of sittings, without trying to memorize; the aim is a feel for the whole system. Then reread the same ten lectures slowly, using the "Heads up!" boxes and the highlighted passages to check what each lecture establishes, and redraw the cumulative summary figure from memory. Lectures 11–17 can then be read in any order as worked examples, or alongside the matching topics in a lecture course.

In a semester course, use the book as a companion: before each block of lectures on a topic, reread the corresponding Sompayrac lecture to keep the big picture in view while the detail is filled in. Keep the glossary and the list of acronyms at hand. Because the book contains no questions, test yourself with the review material of a fuller textbook such as Basic Immunology, and try explaining each lecture's argument aloud in your own words before moving on.