A case of selective IgM deficiency: isotype-specific suppressor T lymphocytes.

A case of selective IgM deficiency with giant leiomyoma of the stomach in a 66-year-old male is reported. Peripheral blood mononuclear cells from the patient synthesized only a small amount of IgM in the presence of pokeweed mitogen (PWM) in vitro. Co-culture of counterpart lymphocytes from the patient and a disease-free individual revealed that increased activity of IgM-specific suppressor T lymphocytes led to a IgM deficiency in this case.