CorpusHuman Anatomy
Lymphatic & ImmuneCell

Memory lymphocytes

Also known as: memory cells, memory B cells, memory T cells, central memory T cells, effector memory T cells, tissue-resident memory T cells

Long-lived antigen-experienced B and T cells, left behind after an immune response, that are more numerous, more easily activated and faster-acting than naive cells — the cellular basis of immunological memory and vaccination.

Adaptive Immune Response

Overview

After clonal expansion, most effector cells die once the antigen is cleared (contraction, ≈ 90–95%), but a fraction survive as memory cells. The pool of cells specific for a given antigen is then 10–1000 times larger than before; the cells respond to lower antigen doses, depend less on co-stimulation, and acquire effector function within hours to days rather than a week. Memory is maintained for years to decades: memory T cells undergo slow homeostatic proliferation driven by IL-7 and IL-15, independent of antigen, and long-lived plasma cells in the bone marrow keep secreting antibody ("serological memory").

Memory B cells are mostly class-switched (IgG, IgA, IgE) and carry somatically mutated, high-affinity receptors; on re-exposure they rapidly differentiate into plasma cells or re-enter germinal centres. Memory T cells (CD45RO⁺) form three main groups: central memory (T_CM; CCR7⁺ CD62L⁺) that patrol lymphoid organs and have great proliferative capacity; effector memory (T_EM; CCR7⁻) that circulate through blood and tissues ready for immediate effector function; and tissue-resident memory (T_RM; CD69⁺, often CD103⁺) that remain in barrier tissues such as skin, gut and lung as a front-line guard.

Location

Lymphoid organs (central memory), blood and tissues (effector memory), barrier tissues (tissue-resident memory), bone marrow (memory T cells and long-lived plasma cells).

Parts & subdivisions

  1. Memory B cells
    High-affinity, mostly class-switched; generate the rapid IgG-dominated secondary antibody response.
  2. Long-lived plasma cells
    Not memory cells in the strict sense, but sustain protective antibody titres from bone-marrow niches.
  3. Central memory T cells
    CCR7⁺; reside in lymphoid organs; proliferate vigorously on recall.
  4. Effector memory T cells
    CCR7⁻; patrol peripheral tissues; rapid cytokine production and cytotoxicity.
  5. Tissue-resident memory T cells
    Non-circulating cells lodged in skin, mucosae and other tissues.

Function

  • Provide faster, larger and higher-affinity secondary responses on re-exposure to the same antigen.
  • Underpin long-term protection after infection and vaccination.

Clinical significance

Vaccination and boosters

Vaccines aim to generate memory without disease. Boosters re-stimulate memory cells to raise antibody titres and affinity. Memory after smallpox vaccination can persist for more than 50 years, whereas protection against some pathogens (pertussis, influenza variants) wanes or is evaded by antigenic change.

Measles "immune amnesia"

Measles virus infects memory lymphocytes (via the receptor CD150/SLAM) and can erase a substantial part of pre-existing antibody repertoires, leaving children vulnerable to other infections for months to years — an additional argument for measles vaccination.

Compiled from standard anatomy and physiology references — see the Lymphatic & Immune System sources. For education only; not medical advice.