Figure 2.

B-cell development in man. Transitional B cells in the spleen potentially mature into three B cell subsets: (i) CD5⁺ mature naïve B cells; (ii) conventional mature naïve B2 or FO B cells; and (iii) marginal zone (MZ) B cells which contain mutated IgV genes possibly aquired in a T-cell independent manner. After antigen recognition, mature naïve B2 cells engage in T-cell dependent germinal center (GC) reactions in which SHM and CSR occur, generating high-affinity class-switched memory B cells and plasma cells (PC).