Serum IgG and renal transplantation.

In 57 patients with renal allografts the prolonged administration of prednisolone >/= 1 mg/kg/day and azathioprine >/= 3 mg/kg/day caused a significant and persistent fall in serum IgG at all levels of creatinine clearance. The fall in IgG was more striking when creatinine clearance was below 25 ml/min. At lower doses of azathioprine and prednisolone serum IgG fell when the creatinine clearance was less than 35 ml/min, the degree of recovery towards normal being dependent on creatinine clearance and dosage. Post-transplant haemodialysis decreased the depression of IgG, and patients with immediately functioning grafts had minimal IgG depression. An inverse relation between IgG and IgM was observed in some patients. Severe infections and toxicity were associated with the greatest reduction in IgG; leucopenia and thrombocytopenia were not consistently reliable guides to toxicity. The deaths of four patients (7%) were associated with severe infections. Falls in IgG were not related to the rejection process. IgG measurement should be used as a guide to immunosuppression and toxicity in renal allograft patients.