Stimulation of B and T cells by in vivo high dose immunoglobulin administration in normal mice.

Adult BALB/c mice were injected intravenously with a preparation of pooled normal murine IgG (400 mg/kg/day, on five consecutive days) and studied 8, 15, and 60 days later. High dose IgG administration increased the total numbers of splenic activated B and CD4+ (but not CD8+) T cells, as well as the numbers of splenic Ig-secreting cells, particularly in the IgG isotypes. Reactivities to some autoantigens, but not to bacterial or other heteroantigens, were selectively amplified amongst IgM-secreting cells. IgG administration did not alter the specific primary immune response to heterologous erythrocytes or bacterial dextran. No cellular alterations were detected in the lymph nodes or peritoneal cavity of treated animals. Most of these effects subsided with time, but some autoantibody reactivities remained elevated 60 days later. The present results suggest that the therapeutic effects of high dose IgG administration which have been reported in human diseases might be associated with the immunostimulatory activities of such treatment.