Increased IgM and IgM immune complex-like material in the circulation of renal transplant recipients with primary cytomegalovirus infections

Twelve of 60 consecutive adult recipients of cadaver kidney transplants had increased polyethyleneglycol (PEG) precipitable IgM immune complex-like material in their circulation in the first 4 months after transplantation. All 10 recipients with primary CMV and two of four with secondary CMV infections had significant elevations in PEG precipitable IgM that coincided with rises in their CMV antibody titres. Ultracentrifuge analysis demonstrated two peaks of PEG precipitable material with sedimentation rates of about 20S and 40S. Total IgM immunoglobulin levels also were increased in transplant recipients with CMV infections, but this was less specific and occurred in patients without CMV infections. The C1q binding assay, which is more sensitive for IgG and IgM containing complexes, was positive in only three of 10 patients with primary CMV and none of four with secondary CMV. Granular deposits of IgM, but not IgG, were detected in the glomeruli of six of seven transplants biopsied during CMV infection. The PEG-IgM assay was not influenced by rejection or prednisone therapy. Thus, transplant patients, who develop primary CMV infections, produce elevated levels of circulating IgM and IgM immune complex-like material. These findings may help to differentiate CMV infection from transplant rejection as well as to increase our understanding of the special pathogenic properties of CMV in transplant recipients.