Anti-host cytotoxic T cells of bone marrow transplant recipients with or without graft-versus-host disease are equally sensitive to cyclosporin A.

It is generally accepted that cytotoxic T cells (CTLs) play an important role in the pathogenesis of graft-versus-host disease (GVHD). Nonetheless, anti-host CTLs can be observed in the peripheral blood of patients both with and without clinical signs of GVHD following HLA genotypically identical bone marrow transplantation. Thus we questioned whether a qualitative difference, such as a differential in vitro sensitivity to cyclosporin A (CsA), may exist between the anti-host CTLs, generated from these groups of patients post-bone marrow transplantation (BMT). We analyzed anti-host CTL precursors (CTLp) of patients without clinical signs of GVHD, of patients suffering from acute GVHD (grade II-IV) and of patients suffering from acute GVHD followed by chronic GVHD for their in vitro sensitivity to the inhibitory effects of CsA. The results obtained in a total of 20 patients revealed anti-host CTLp frequencies (CTLpf) post-BMT in all three groups of patients and addition of CsA in the tests resulted in approximately 60% inhibition of the CTLpf independent of the GVHD status of the patients. Thus, in view of the in vitro CsA sensitivity, no difference exists between the anti-host CTLs in patients with or without GVHD.