Functional and morphological suppressor T cell deficit in acute GVHD.

Bone marrow transplantation (BMT) is currently used to treat patients with severe haematological disorders. One of its major complications is acute graft versus host disease (aGVHD). In this report we show that, during the early stages of lymphoid cell repopulation, an excess of suppressor T cell activity and a deficit of helper T cell activity are easily demonstrated by functional studies in healthy BMT recipients. On the contrary, in patients with active signs of aGVHD, a loss of suppressor T cells, as assessed by coculturing recipient T cells with donor B cells in an in vitro pokeweed mitogen (PWM) dependent Ig secreting assay, is detected. The loss of suppressor T cells in these patients is revealed also by the analysis of peripheral blood lymphocytes with the OKT5 suppressor cytotoxic monoclonal antibody (MoAb) but not with the OKT8 suppressor cytotoxic MoAb. Our data demonstrate that in several BMT recipients, during active aGVHD, a suppressor T cell deficit can be demonstrated both functionally and phenotypically.