Human normal CD5⁺ B lymphocytes can be induced to differentiate to CD5^- B lymphocytes with germinal center cell features

A significant proportion of cord blood CD5⁺ B cells express the activation molecules CD23, CD25, and transferrin receptor; react with the cell-cycle-associated monoclonal antibody (MoAb) Ki67; can be induced to enter the S phase of cell cycle by interleukin-2 (IL-2), IL-4, or low-molecular-weight B-cell growth factor (lmw-BCGF) and, exposed to IL-1 and IL-2, acquire the features (sIgD^-, CD5^-, CD10⁺, CD38⁺) of B blasts proliferating in the germinal centers of secondary follicles. These findings indicate that CD5⁺ B cells are preactivated and, in the proper microenvironment, may give rise to CD5^-B cells.