DIFFERENCE IN THE EXPRESSION OF FAS FAS-LIGAND AND THE LYMPHOCYTE SUBSET RECONSTITUTION ACCORDING TO THE OCCURRENCE OF ACUTE GVHD/

Acute graft-versus-host disease (aGVHD) remains a major barrier to a w ider application of allogeneic bone marrow transplantation (BMT), Alth ough this complication is mainly dependent on donor-derived T lymphocy tes, very little information is available concerning the mechanism of lethality, In this study, we investigated both the expression of Fas/F as-ligand (FasL) and lymphocyte subset reconstitution in patients who underwent HLA-matched related allogeneic BMT (n = 16) and normal donor s (n = 10), and several distinct features were observed, First, the re constitutions of CD3(+) and CD56(+) cells were different between the a GVHD(+) and aGVHD(-) group, In particular, the percentage of CD3(-)CD5 6(+) cells was significantly decreased in patients with aGVHD (P < 0.0 1), Second, the expansion of CD8(+) (P = 0.01) and CD8(+) CD28(-) T ce lls (P = 0.03) was a characteristic finding in patients with aGVHD, Fi nally, we found that the percentages of Fas(+)CD8(+), Fas(+)HLA-DR+ an d FasL(+) CD8(+) cells were significantly increased, Fas antigen was h ighly coexpressed on most of the lymphocyte subsets, especially on CD8 (+) cells (P < 0.01), and also, significantly higher coexpression of F ast on CD8(+) cells was found in patients with aGVHD (P < 0.01), In su mmary, an increase in the percentage of CD8(+) cells which express Fas and its ligand in patients with aGVHD after BMT points to a possible role for the Fas/FasL pathway in the effector phase of aGVHD.