The formation of immunoglobulins by human tissues in vitro. IV. Circulating lymphocytes in normal and pathological conditions.

The formation of immunoglobulins by circulating lymphocytes was studied by three techniques: (1) Autoradiographic analysis of the immunoglobulins synthesized during the incubation of cell suspensions in a medium with radioactive amino acids; (2) direct immunofluorescent staining; and (3) examination of the cellular morphology. Lymphocytes of the normal peripheral blood were found to synthesize a distinct amount of IgG and smaller amounts of IgA and IgM. Cells of the thoracic-duct lymph synthesized distinct amounts of all three immunoglobulins. A similar pattern was found in infectious mononucleosis and rubella. In infectious mononucleosis the significantly increased synthesis of IgM during the first 10 days of illness led to the supposition that this result may be due to primary antigenic stimulation. The pattern in chronic lymphatic leukaemia is characterized by the consistent absence of IgA and the labelling of IgG, mainly the medium to high mobility part, and of IgM. In agammaglobulinaemia a trace of IgG and IgA was found in one case; the other was entirely negative. The immunofluorescent staining showed that in all samples some of the medium-sized lymphocytes contain IgG, IgA or IgM. Peripheral blood samples taken during an infectious mononucleosis or rubella infection and thoracic duct lymph revealed also positive large lymphocytes and plasma cells. A remarkable observation was the weak fluorescence of small lymphocytes which were exclusively positive for IgM. It is postulated that these small lymphocytes indicate their initial synthesis of IgM antibodies when engaged in primary response.