Germinal center

A germinal center is a temporary structure in lymphoid tissue where activated B cells proliferate, mutate their antibody genes, and undergo selection for improved antigen binding.

Somatic hypermutation: A process that introduces mutations into antibody variable-region genes in activated B cells. It generates antibody variants that germinal-center selection can test.
B cell: A lymphocyte that recognizes antigen through a B-cell receptor and can produce antibodies. Activated B cells are the cells that enter and develop within germinal centers.
Vaccine: A preparation that trains the immune system to recognize a pathogen or other target. Many vaccines seek durable, high-affinity antibody responses produced through germinal-center reactions.
Memory B cell: A long-lived B cell that responds rapidly when it encounters its antigen again. Some germinal-center B cells leave the reaction as memory cells.
Affinity maturation: The gradual increase in the average antigen-binding strength of antibodies during an immune response. Germinal-center selection enriches B cells whose antibodies bind antigen more strongly.
Lymphoid follicle: A B-cell-rich compartment in a lymphoid organ, sometimes containing a germinal center. Germinal centers arise inside follicles after suitable immune stimulation.
Monoclonal antibody: An antibody preparation derived from one B-cell lineage and directed against a particular target. Germinal-center selection inspires methods for evolving antibodies with improved binding.
Immunoglobulin class switching: A DNA recombination process that changes an antibody's constant region while preserving antigen specificity. Germinal-center B cells can switch antibody class to alter effector function.
AID: An enzyme that initiates somatic hypermutation and class-switch recombination in activated B cells. AID creates the antibody-gene changes that drive germinal-center diversification.
Follicular dendritic cell: A stromal cell that retains intact antigen in lymphoid follicles and presents it to B cells. It displays antigen that germinal-center B cells compete to capture.

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