Self & Other
19. A Glossary of Medical News
This chapter is a reference. It is here so that, the next time you read a news article about a new biologic, a checkpoint inhibitor, a cytokine storm, or some other term that medical journalism uses without explaining, you have somewhere to go.
The list is not exhaustive. It is the set of words that appear regularly in mainstream coverage of immunology, infectious disease, vaccines, autoimmune conditions, and cancer treatment. Most of them have appeared somewhere in the previous chapters. Some are repeated here, with shorter, more useful definitions for quick reference. The voice here is more clipped than in the rest of the book, on purpose. You can read this chapter straight through if you want, or you can come back to it whenever you need it. Most readers, I expect, will use it as a kind of standing reference.
A general note before we start. Most medical jargon was originally created to be precise, not to confuse. The Greek and Latin roots make sense once you know them. A “phago-cyte” is an eating cell. A “lympho-cyte” is a cell of the lymph system. An “im-mun-o-globulin” is an immune-related globular protein. A “cyto-kine” is a cell-mover. The vocabulary becomes much less intimidating once you start hearing the underlying parts.
The Cells
Names of immune cells you will encounter in news articles. We met all of them in Chapters 2, 3, and 7.
Macrophage. A large white blood cell that lives in tissues and eats things — bacteria, dead cells, debris. Also a major source of cytokines, the chemical signals that coordinate the rest of the immune response. Different tissues have different specialty macrophages with different names: Kupffer cells (liver), microglia (brain), osteoclasts (bone).
Neutrophil. The most abundant white blood cell. Short-lived, fast, aggressive. The first cells to swarm a wound or infection. Pus is mostly dead neutrophils.
Dendritic cell. A long-armed cell that lives in tissues, samples its surroundings, and carries fragments of any foreign material it finds to the nearest lymph node, where it presents them to T cells. The bridge between innate and adaptive immunity.
B cell. A type of lymphocyte (a small white blood cell) that, when activated by a matching antigen, produces antibodies. Each B cell has its own unique antibody, generated by the V(D)J shuffling we discussed in Chapter 3.
Plasma cell. An activated B cell in full antibody-production mode. The cellular factories that flood the bloodstream with antibodies during an infection.
T cell. A type of lymphocyte that recognizes fragments of antigens displayed on other cells’ MHC molecules. Three main flavors: helper T cells (which orchestrate the response), killer T cells (which destroy infected or cancerous cells), and regulatory T cells (which calm the response down).
Treg. Short for regulatory T cell. Often pronounced “tee-reg.” A T cell whose job is to suppress immune responses, keeping the system from attacking harmless things or itself.
NK cell. Natural killer cell. An innate-immunity counterpart to killer T cells, looking for cells that have stopped displaying their normal MHC molecules — often a sign of viral infection or cancer.
Mast cell. A tissue-resident cell loaded with granules of histamine and other chemicals. When triggered, often by IgE binding its target, the mast cell dumps its granules into the surrounding tissue. Responsible for most allergy symptoms.
Eosinophil. A white blood cell specialized for fighting parasites and involved in some allergic responses. Elevated eosinophil counts in blood tests often signal allergy or parasitic infection.
Microglia. Macrophages of the brain. They patrol brain tissue, clear debris, and respond to damage or infection. Increasingly implicated in neurodegenerative diseases and depression.
The Molecules
Proteins and other small molecules that show up in news articles about immunology and disease.
Antigen. Anything the immune system recognizes and responds to. A protein on a virus, a fragment of a bacterial wall, a peanut protein, a piece of someone else’s tissue. The general term for “thing the immune system pays attention to.”
Antibody. A Y-shaped protein produced by B cells that binds to a specific antigen with very high precision. Antibodies neutralize, mark for destruction, or otherwise mark out their targets. Also called immunoglobulin or Ig.
Antibody classes (IgG, IgM, IgA, IgE, IgD). Five major flavors of antibody, each suited to a different role. IgG is the most abundant, the workhorse of long-term immunity. IgM is the first antibody made in a new infection. IgA is concentrated at mucosal surfaces (gut, airways, breast milk). IgE drives allergic reactions and parasite defense. IgD is the one nobody has fully figured out.
Monoclonal antibody. A laboratory-produced antibody, derived from a single B cell line, that binds one specific target. The basis of an entire class of modern drugs (rituximab, adalimumab, pembrolizumab, and many others). Drugs whose names end in “-mab” are monoclonal antibodies.
Autoantibody. An antibody that recognizes one of the body’s own proteins. Autoantibodies are characteristic of autoimmune diseases. Their presence in blood tests can confirm or suggest specific conditions — anti-thyroid antibodies in Hashimoto’s, anti-nuclear antibodies in lupus, anti-CCP in rheumatoid arthritis.
Neutralizing antibody. An antibody that, by binding to a virus, physically prevents the virus from entering cells. The kind of antibody most relevant to vaccines that prevent viral infection.
Cytokine. A small protein released by immune cells (and others) to send signals to other cells. Cytokines coordinate the immune response: who shows up, where, in what numbers, and how vigorously they respond. There are dozens of named cytokines, each with its own role. TNF, IL-1, IL-6, IL-17, the interferons, and many others.