Delayed detection of cytomegalovirus-specific T-helper cells in a preterm infant following intrauterine exposure to tacrolimus.

After exposure to tacrolimus and CMV reactivation in utero, a preterm infant had a positive CMV polymerase chain reaction (PCR) in urine on day 2 of life. Naive T-cells were reduced, but stimulation with CMV antigen and a polyclonal T-cell activator in vitro yielded no measurable CD4+ T-cell response. When repeated on day 30, polyclonal activation was in the range of healthy adults, while the immune response to CMV was incomplete with a lack of IFNgamma+ CD4+ T-cells and no anti-CMV IgM. Thus, exposure to tacrolimus in utero caused a transitional T-cell activation defect which did not compromise viral clearance.