Selective IgM deficiency in adults: phenotypically and functionally altered profiles of peripheral blood lymphocytes.

Peripheral blood lymphocytes from four patients with selective IgM deficiency were examined phenotypically and functionally. Although B cell subpopulations determined by surface immunoglobulins were within normal or nearly normal range, T8+ cells were significantly increased and T4/T8 ratios were inverted in three patients. IgM specific hyporesponsiveness in the PWM-driven immunoglobulin production system was observed in all four patients. Ia-like antigen positive T cells were increased in two patients; both had increased Leu2a+ Leu15+ suppressor-effector cells. In addition, Leu3a+ Leu8+ suppressor-inducer cells were increased in one of these two patients. Excessive (either IgM-specific or isotype non-specific) suppressor activity of T cells and IgM specific hyporesponsiveness of non-T cells were observed in these two patients in the recombination plaque assay. Although these results showed the complexity of the pathogenesis of this syndrome, they suggested that suppressor-associated T cells may play a role in some patients with selective IgM deficiency.