Advanced Course in Immunology On Demand Lecture Recordings-B Cell Memory

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Video Summary

The lecture explains how B cells find antigen, get T cell help, and develop into plasma cells and memory cells. Because antigen-specific B cells are extremely rare, the immune system uses secondary lymphoid organs to concentrate antigen and lymphocytes together. In lymph nodes, small antigens can diffuse directly into B-cell follicles, while larger antigens are trapped by subcapsular sinus macrophages and presented intact to B cells. Blood-borne antigens are sampled in the spleen, where marginal zone B cells help move them into follicles.<br /><br />Once a B cell binds antigen, it can activate and migrate toward the T-cell zone by upregulating CCR7; activated T cells upregulate CXCR5 and move toward the B-cell zone. This allows cognate B-T interactions through linked recognition: B cells internalize antigen, present peptide on MHC II, and receive help from T follicular helper cells via costimulatory molecules and cytokines. These interactions drive two main early outcomes: short-lived extrafollicular plasma cells and germinal centers.<br /><br />Inside germinal centers, B cells mutate their receptor genes and are selected mainly by competition for T cell help in the light zone, not simply by stronger BCR signaling. This selection is important for affinity maturation and may also reduce autoimmunity by requiring cognate T-cell support.<br /><br />The lecture then covers long-lived plasma cells and memory B cells. Long-lived plasma cells, mostly in bone marrow, secrete antibodies for years or even decades. Memory B cells are heterogeneous: some mainly restart germinal centers, while others rapidly generate plasma cells on re-exposure. The talk ends with examples of tissue-resident memory, atypical memory B cells, and DN2 cells, which are important in infection and autoimmunity.

Asset Subtitle

Lecture 12: Deepta Bhattacharya, University of Arizona

B Cell Memory

Asset Caption

Deepta Bhattacharya, University of Arizona
B Cell Memory

Keywords

B cells

antigen presentation

secondary lymphoid organs

lymph nodes

spleen

T cell help

germinal centers

plasma cells

memory B cells

affinity maturation

T follicular helper cells

autoimmunity