Monoclonal immunoglobulins in patients with renal transplants: characterization, evolution and risk factors.

Gammopathies were found to be present in 25 (13%) of 192 HIV-negative renal transplant recipients with more than 30 months follow-up prospectively investigated for monoclonal or oligoclonal immunoglobulins (mIg) by agarose gel electrophoresis and immunofixation. Eleven patients had only one monoclonal band, whereas 14 had two or more bands. Of these bands, 60% were IgG kappa, 29% IgG lambda and 11% IgM lambda or kappa, and 90% did not exceed 2 g/l. Most gammopathies occurred early post-transplant (median 5 months) and they were always transient. Some predisposing factors for mIg emergence could be identified: 1. age, but only in women, 2. duration of dialysis, 3. occurrence of prior cytomegalovirus infection, and 4. immunosuppressive regimen including cyclosporine. Serological evidence for active EBV infection was obtained in ten patients, but in six cases infection occurred subsequent to the finding of mIg. In eight patients, the clinical course was characterised by severe infection or tumours (one Kaposi's sarcoma, one B-cell brain lymphoma). The present findings and experimental studies support the view that the development of mIg in renal transplant patients is associated with a failure of regulatory T-cell function. This T-B-cell imbalance requires a careful follow-up in these patients.