BACKGROUNDSpecific anticytomegalovirus (anti-CMV) intravenous immunoglobulin (IVIG) has the potential to influence the immune response, but its complex mode of action has not been well evaluated.METHODSAn immunologic study of 6 CMV-seronegative heart transplant patients receiving anti-CMV prophylaxis with the use of ganciclovir and CMV-IVIG (150 mg/kg within 24 hours after transplantation and 100 mg/kg on days 2, 7, 14, 22, 35, 56, and 77 after transplantation) was performed in a single center. Lymphocyte subsets were evaluated by means of 4-color flow cytometry at the time of inclusion in the waiting list and at 3 months after transplantation.RESULTSHigh-risk heart recipients receiving CMV-IVIG showed a clear reduction in the frequency of activated CD4+CD38+DR+ T-helper cells at 3 months after transplantation compared with a group of 27 untreated control subjects who received only anti-CMV prophylaxis with the use of ganciclovir. In this study, an increase of CD19+CD27-IgM+IgD+ naïve B cells was also observed in seronegative recipients after prophylaxis with the use of CMV-IVIG but not in control subjects. None of the CMV-IVIG-treated recipients developed acute cellular rejection during the 1st 6 months after transplantation.CONCLUSIONSThe immune modulation of activated CD4+ lymphocyte and of naïve B-cell subsets after CMV-IVIG use should be further evaluated in future prospective studies with higher numbers of patients.