Some effects on leukaemic B lymphocytes of antibodies to defined regions of their surface immunoglobulin.

During the growth of the L2C leukaemia in strain 2 guinea-pigs there is excreted in the urine a monoclonal light chain of lambda class. This is believed to arise from synthesis by the leukaemic cells of a small molar excess of the light chains incorporated into their surface IgM. Antibodies to this light chain have been raised in rabbits and separated by immunosorption into those directed against idiotypic determinants (anti-Id), and those against determinants also present on other lambda chains (anti-lambda). Both antibodies react with L2C cells via the surface immunoglobulin. In accord with prediction anti-Id is specific for L2C cells while anti-lambda also reacts with 7 per cent of normal nodal lymphocytes. L2C cells are agglutinated strongly by anti-Id, weakly by anti-lambda. Both antisera inhibit migration of the cells, and both can kill them by invoking complement or K-cell cytotoxic mechanisms. The results emphasize the potential of anti-idiotype sera for identifying and specifically attacking neoplastic B lymphocytes.