Anti-Idiotypic B Lymphocytes in Patients with Monoclonal Gammopathies

The prevalence of peripheral blood B cells secreting antibodies reacting with the F(ab')2 fragment of monoclonal IgG was studied in five patients with multiple myeloma (MM), nine patients with monoclonal gammopathy of undetermined significance (MGUS) and six healthy controls. An enzyme-linked immunospot assay allowed direct visualization of antibody producing B cells. All patients had B cells producing antibodies to autologous or allogeneic monoclonal IgG. Autoreactive cells were found more frequently than alloreactive cells in seven out of nine patients with MGUS and three out of four patients with MM. The same frequency of alloreactive cells in the patient groups was detected in healthy individuals. These findings show the existence of B cells producing anti-idiotypic antibodies which could be a part of an idiotypic network in monoclonal gammopathies.