Memory B Cell
Definition
A long-lived B cell generated during a primary immune response that retains the antigen-specific receptor and persists in lymphoid tissue. On re-exposure to the same antigen, memory B cells respond rapidly without the lag of the primary response, producing high-affinity IgG in large quantities.
- Origin
- Primary immune response
- Lifespan
- Long-lived, resides in lymphoid tissue
- Response speed
- Rapid, no primary-response lag
- Antibody produced
- High-affinity IgG in large quantities
Common questions
How does a memory B cell response differ from a first-time infection response?+
A first exposure requires naive B cells to be found, activated, and expanded, which takes days and initially produces lower-affinity IgM. Memory B cells skip that search and expansion delay because they already carry the antigen-specific receptor, so IgG appears faster and at higher affinity.
Why does this matter for interpreting a serology result in a forensic case?+
A rapid, high-titre IgG response on re-testing can indicate prior exposure rather than a new infection, which is relevant when timing an exposure event is part of the analysis. Antibody kinetics driven by memory cells can make exposure timing harder to pin down from a single sample.
Related terms
- Affinity Maturation
- The progressive increase in antibody-antigen binding strength that occurs during the secondary and subsequent responses. It results from somatic hypermutation of immunoglobulin...
- Clonal Selection
- The process by which an antigen binds selectively to the lymphocyte (B or T cell) that carries the complementary surface receptor, triggering...
- Cytotoxic T Cell (CTL)
- A CD8+ T lymphocyte that recognises peptide antigens presented on MHC class I molecules and kills the target cell by releasing perforin...
- Helper T Cell
- A CD4+ T lymphocyte that recognises antigen on MHC class II molecules and secretes cytokines that amplify both the humoral and cellular...
- Plasma Cell
- A terminally differentiated B cell that has lost most of its surface immunoglobulin and become a high-output antibody factory, secreting thousands of...