In vitro idiotypic suppression of chronic lymphocytic leukemia lymphocytes secreting monoclonal immunoglobulin M anti-sheep erythrocyte antibody.

A patient with chronic lymphocytic leukemia was found to have B cells with surface immunoglobulin (Ig)M manifesting anti-sheep erythrocyte (SRBC) specificity together with a high titer serum monoclonal anti-SRBC IgM antibody. By immunizing a sheep with the monoclonal IgM antibody, followed by multiple absorptions against normal human IgM, an anti-idiotype (Id) antibody was obtained. The serum IgM anti-SRBC antibody was then demonstrated to share the same idiotypic determinants with the surface IgM with anti-SRBC specificity on the patient's B cells. The anti-Id antibody suppressed the spontaneous secretion of anti-SRBC antibody as well as the pokeweed mitogen-induced anti-SRBC antibody production as measured by a hemolysis-in-gel plaque-forming cell assay. In contrast, pokeweed mitogen-induced anti-SRBC plaque-forming cell responses of normal individuals were not suppressed by the anti-Id antibody. Thus, this study demonstrates in vitro suppression of human B-cell function by anti-Id antibody.