Abstract
Ten patients with selective IgM deficiency (SIgMD) were studied for cell surface immunoglobulin, immunophenotype of T lymphocytes and immunoglobulin synthesis in vitro by peripheral blood lymphocytes. Serum IgM levels were less than 25mg/dl, while IgA, IgG, and IgD were within normal levels. Ten patients had respiratory or urinary tract infections, three were diagnosed as having systemic lupus erythematosus (SLE) and one as rheumatoid arthritis (RA). Surface immunoglobulins were almost within normal range except two cases who had very low surface immunoglobulins. However, normal values were detected after 7 days of culture in the presence of normal T lymphocytes with Pokeweed mitogen. E rosett counts were normal in all patients. As for immunophenotype of T lymphocytes, OKT4/OKT8 ratios were low in all the cases. Analysis of lymphocyte function for immunoglobulin synthesis in vitro, using a co-culture of counterpart T and B cells from healthy individuals and patients with SIgMD, revealed the excessive function of IgM specific suppressor T lymphocytes. These results suggest that the increased function of IgM specific suppressor T cells was responsible for the IgM deficiency in all ten cases.
