Maturational and functional diversity of human B lymphocytes delineated with anti-Leu-8

Human B lymphocyte subpopulations distinguished by their expression of the Leu-8 antigen were studied and found to differ in their respective maturational state and functional repertoire. The absence of Leu-8 expression correlated with an early step in antigen-driven B cell differentiation in that 1) as presented in the companion paper, germinal center B lymphocytes were uniformly Leu-8^-, whereas mantle zone B cells were virtually all Leu-8⁺; 2) treatment of Leu-8⁺ B cells with the combination of rabbit anti-human μ-chain and B cell growth factor (BCGF), but not with either reagent alone, caused the loss of Leu-8 expression in addition to causing these cells to proliferate; and 3) only the Leu-8^- B cell subset contained cells expressing the 4F2 activation antigen. Functional studies of peripheral blood B cells revealed that B cells giving rise to antibody-forming cells in the presence of T cells and pokeweed mitogen (PWM) were found almost exclusively in the Leu-8^- subset of B cells, even though this subset comprised a minority of circulating B lymphocytes. By contrast, Leu-8⁺ B cells proliferated more vigorously than Leu-8^- B cells to formalinized Staphylococcus aureus Cowan I (SAC). These data demonstrate that Leu-8 is an important maturational and functional marker for human B lymphocytes.