Polypeptides on human B lymphocytes associated with cell activation.

Two monoclonal antibodies (MoAbs), designated BB-1 and LB-2, react with distinct polypeptides expressed on activated human B cells. The BB-1 MoAb reacted with a 37,000-dalton polypeptide (Bp37) restricted to pre-B and B-cell blasts and B-cell malignancies. The LB-2 MoAb reacted with a 76,000-dalton polypeptide (p76) found on resting B cells but at higher levels on activated B cells and T cells. Buoyant tonsillar lymphoid cells with a germinal center phenotype express higher levels of Bp37 and p76 than do dense B cells of the mantle zone. Furthermore, the expression of Bp37 and p76 on tonsillar B-cell subsets was distinct from other B-cell antigens such as Bp39, Bp95, Bp135, the C3d receptor and surface IgM. Based on biochemical, cross-blocking, and tissue distribution analyses, these antigens appear to be distinct from previously described B cell and B-cell-blast markers.