Surface markers of human lymphocytes.

The large accumulation of data on serum immunoglobulins (Igs) has made it possible to delineate readily the special membrane Ig receptors that respond to antigenic stimulation. B type lymphocytes are characterized by the selective presence of IgM and IgD. IgG, the main serum Ig, is rarely found and its previous reported presence was due to secondary adsorption. IgM and IgD occur together on the same lymphocytes and show similar or identical variable regions and antigen combining sites. The membrane Igs are positioned on the lymphocyte surface with a cosiderable part of the C-terminal portion of the heavy chains buried in the membrane. In addition to numerous other lymphocyte membrane markers, recent interest has centered on the new histocompatibility surface antigen, HL-B, which appears related to immune response genes and is selectively represented on B cells. Through the use of this group of lymphocyte markers considerable information on the character of the malignant cells in various leukemias and lymphomas has been obtained. Chronic lymphatic leukemia is essentially a proliferation of B cells. Acute lymphoblastic leukemia falls into two groups, a minor type that represents a proliferation of T cells and a major type that appears to show an immature cell type of probable B cells lineage. Various immunodeficiency syndromes have been clarified considerably through lymphocyte analyses and certain defects have been determined.