Early increase of peripheral B cell levels in kidney transplant recipientswith CMV infection or reactivation

Background. Cytomegalovirus (CMV) infection or reactivation is a frequent c omplication of renal transplantation. Diagnosis of these conditions relies on the detection of circulating antigen, or of specific IgM and/or IgG, whi ch develop over several weeks. Evocative clinical features may be detected earlier, but lack specificity. Rapid and early changes in the partition of lymphocyte subsets could be an additional indication of pending CMV infecti on. Methods. A systematic follow-up of peripheral B lymphocytes identified immu nophenotypically by the determination of surface immunoglobulins (sIg), per formed in 97 kidney transplant recipients, allowed to identify transient in creases apparently predictive of CMV prime-infection or reactivation over t he next 3 months. To better define the nature of these B cells, an extended investigation was performed for 14 prospective patients. In addition to su rface Ig, membrane CD19, HLA-DR, and CD80 expression were explored. The cyt oplasmic presence of mu, kappa, and lambda chains was also examined. B cell function was investigated using the ELISPOT technique, which allows an enu meration of the populations of IgG, IgA, and IgM secreting B cells. Results. Retrospective analysis of the clinical outcome of the cohort of 97 patients evidenced that early transient increases in B cell levels were si gnificantly (P < 0.0001) associated with CMV infection. The same trend was noted in the smaller series of patients who benefited from a more extensive investigation of B cells, 10 of whom presented clinical or biological sign s of CMV infection. Mature B cells, expressing surface Ig, CD19, DR, and CD 80 are those presenting transient increases. No significant variation of pr eB (c mu+/kappa lambda-) or activated (spot-forming) cells was evidenced in these patients. Conclusion. Individual examination of each patient's immune reconstitution profile allows to detect transient peaks of mature B cell during the initia l immunosuppressive therapy, that appear to be predictive of oncoming CMV i nfection or reactivation.