The effect of cytomegalovirus infection on T lymphocytes after allogeneic bone marrow transplantation.

The influence of cytomegalovirus (CMV) infection on peripheral T lymphocyte repopulation was studied in 59 bone marrow transplant (BMT) recipients who received either cyclosporin A (CyA) or methotrexate (MTX) as prophylaxis for acute graft-versus-host disease. We used monoclonal antibodies and single- or double-marker immunofluorescence for the quantitation of T4+, T8+ and HNK1+ T cell subpopulations. CMV infection was serologically diagnosed by an enzyme-linked immunosorbent assay (ELISA), and by viral cultures and histological studies. Among the 52 patients who were evaluable for CMV infection, one had a primary infection and 24 had CMV reactivation/reinfection after BMT. In the latter patients, increases to supranormal levels were observed in T8+ T cells and HNK1+ T cells, both in patients on CyA and in patients on MTX. Double-marker immunofluorescence revealed that the two markers were largely expressed by the same cells, which therefore had the T8+ HNK1+ phenotype. In addition, the very small subset of T4+ HNK+ T cells was slightly, but consistently, increased in the patients with CMV reactivation/reinfection. CMV infection did not influence the numbers of T4+ HNK1- and T8+ HNK1- T cells. The long-lasting presence of large numbers of T8+ HNK1+ T cells in patients who had CMV reactivation/reinfection suggests a continuing interaction between the virus and the immune system of its host.