A comparison of four ultraviolet sources to alter graft-versus-host responses

Graft-versus-host disease (GVHD) is a major contributor to the morbidity and mortality associated with allogeneic bone marrow transplantation. Direct ultraviolet B (UVB) irradiation of bone marrow and spleen cell allografts in mice using broadband lamps is known to abolish alloreactive responses which would normally cause GVHD. Using a histoincompatible murine model, we have extended these observations by comparing the physical spectrum of four UV sources (the Philips TUV8W, TL12 and TL01, and the Spectronics XX15B) with in vitro assessment of bone marrow progenitor cell damage and suppression of lymphocyte proliferation and in vivo comparison of the effect on GVHD of the TL12 and XX15B and on the rate of engraftment with the TL12. At doses of uv found to abolish lymphocyte proliferation (2.5, 7, 12 and 1000 J m(-2) with the TUV8W, XX15B, TL12 and TL01 lamps) colony-forming unit granulocyte-macrophage (CFU-GM) proliferation was reduced to 81%, 71%, 79% and 62%, respectively. At an optimal dose found to suppress GVHD (100 J m(-2) integrated radiant energy from 200-320 nm for the TL12 and XX15B) CFU-GM proliferation showed a reduction of 98% with the XX15B and 86% with the TL12. At this radiant energy with the TL12, the rate of bone marrow engraftment was impaired with 72% marrow cellularity at 2 weeks, decreasing to 48% after 200 J m(-2). Our results with this model demonstrate that broadband UVB irradiation of bone marrow permits transplantation across a major histocompatibility barrier. Furthermore we have provided in vitro evidence that narrowband UVB or UVC might potentially be applied to this model.