B lymphocyte development, heterogeneity, and function

Thymus-independent (B) lymphocytes are a heterogeneous group of cells which, it is increasingly clear, undergo an ordered sequence of differentiation steps from stem cells to antibody producing cells. Through the study of the immunologic potential of B lymphocytes from neonatal mice and from mice with an X-linked immune defect, it has become possible to assign certain functions to cells of distinct differentiated states. Furthermore, a differentiation antigen, Lyb 5, has been identified which acts as a marker of a particular subset of B lymphocytes in normal mice. Initial studies of the functional properties of Lyb 5+ and Lyb 5- B lymphocytes are described.