Monoclonal antibody against a cross-reactive idiotypic determinant found on human autoantibodies with anti-I and -i specificities.

A monoclonal antibody has been raised against a cross-reactive idiotypic determinant expressed on human autoantibodies with anti-I and -i specificities. The McAb is directed against a conformational epitope requiring interaction of H- and L-chains for maximal expression. This epitope was strongly expressed on the monoclonal protein of one out of 100 patients with paraproteinaemia and the peripheral blood lymphocytes of one out of 50 cases of B-cell leukaemia. A small amount of the epitope is detectable among immunoglobulins in normal serum.