B-cell senescence

B-cell senescence encompasses age-related changes in B-cell development, composition, and function that collectively impair humoral immunity. A hallmark is the accumulation of age-associated B cells (ABCs) — a population characterised by expression of T-bet, FcRL5 and CD11c and typically CD21lo/CD27- — which expand preferentially in aging and autoimmune contexts and are poor participants in germinal centre reactions. Germinal centre responses, which are necessary for somatic hypermutation and affinity maturation of antibodies, decline in magnitude and quality with age, resulting in lower-affinity, less class-switched antibody repertoires. These changes contribute to reduced vaccine efficacy and an increased propensity for auto-reactive and low-affinity antibody production in older adults.