Immune System & Aging

B-cell senescence covers the age-related changes in your B cells (the antibody-making immune cells) that weaken your antibody immunity. A hallmark is the buildup of…

The CD4/CD8 ratio compares two kinds of T cell in your blood: CD4+ helper T cells versus CD8+ killer T cells. A healthy ratio is usually cited as about 1.5 to 2.5. In young,…

Clonal hematopoiesis of indeterminate potential (CHIP) means one blood stem cell, carrying a driver mutation, has quietly expanded into a large clone. The usual mutated genes are…

Cytomegalovirus (CMV) is a very common beta-herpesvirus that sets up lifelong latency after the first infection. Seroprevalence runs from about 40 to 70% in high-income…

The complement system is a squad of more than 30 blood and cell-surface proteins that form a fast-acting arm of your innate immune system. It switches on through three routes…

Dendritic cells (DCs) are antigen-presenting cells, made in your bone marrow, that bridge innate and adaptive immunity. Two main types circulate in your blood. Plasmacytoid DCs…

Interleukin-10 (IL-10) is your immune system's main 'calm down' signal. It is an anti-inflammatory cytokine, made mostly by macrophages, regulatory T cells, and B cells. It tamps…

IL-1β (interleukin-1 beta) is a powerful pro-inflammatory cytokine. Your monocytes and macrophages make it. It drives acute inflammation. It also drives 'inflammaging', the…

Immunosenescence is the age-related rewiring of your immune system. Three things drift. Your thymus and bone marrow make fewer fresh (naive) lymphocytes. Older, experienced…

The M1/M2 framework describes two opposite 'modes' your macrophages can switch into. (Macrophages are immune cleanup cells.) M1 macrophages, called classically activated, are…

Your T cells come in two broad camps: naive and memory. Naive T cells have not met their target yet. They constantly circulate through your lymph organs, waiting for their…

Natural Killer (NK) cells are part of your innate immune system. They destroy virus-infected and cancerous cells without needing prior 'training' on an antigen. Their action is…

Plasma cells are fully matured B cells, the body's antibody factories. They drop their B-cell surface markers (including CD79, which partners the B-cell receptor) and ramp up two…

Specialized pro-resolving mediators (SPMs) are your body's 'stop' signals for inflammation. They are bioactive fats made from polyunsaturated fatty acids. Lipoxins come from…

T-cell exhaustion is a worn-out, underperforming state that your antigen-specific T cells (mainly CD8+ killer T cells) fall into when an antigen sticks around too long, as in…

Thymic involution is the slow replacement of your thymus tissue with fat. It starts in early childhood and speeds up at puberty. As it progresses, the thymus makes fewer fresh…

TNF-α (tumor necrosis factor alpha) is a powerful pro-inflammatory signal (a cytokine). It is made mostly by immune cells called macrophages and monocytes, when they sense…

Toll-like receptors (TLRs) are ten receptors, on the cell surface and inside endosomes, that form a primary sensing layer of your innate immunity. The surface TLRs (TLR1, TLR2,…

Trained immunity is the idea that your innate immune cells can 'learn'. The concept comes mainly from Mihai Netea and colleagues. It means your fast-response immune cells (mainly…

T regulatory cells (Tregs) are a specialized subset of CD4+ T cells, defined by a master protein called FOXP3. Their job is to suppress excessive immune responses and keep your…

Type I interferons are your body's first-line antiviral alarm signals. The main ones are IFN-α (many subtypes) and IFN-β. Almost any cell with a nucleus can release them when it…

Vaccines work less well as you age, and several immune changes pile up to cause it. You have fewer fresh (naive) T and B cells, weaker germinal-center reactions, shorter-lived…