Expression of HLA-C-specific natural killer cell receptors (CD158a and CD158b) on peripheral blood mononuclear cells after allogeneic bone marrow transplantation

We investigated the expression of natural killer cell receptors (NKRs) for HLA-C on peripheral blood mononuclear cells (PBMCs) in 23 allogeneic bone marrow transplantation (allo-BMT) patients to analyse the role of NKRs in alloresponse concerning graft-versus-host disease (GVHD). CD158a expression was low and there was little change in the expression after allo-BMT. Also, there was no difference in the proportion of CD158a(+)/CD3(-) after allo-BMT. In contrast, the proportion of CD158b(+)/CD3(-) cells, mainly NK cells, increased in the early stage (<2 months) after allo-BMT and then gradually decreased (3.3 +/- 2.6% before BMT vs. 15.4 +/- 8.6% in the early stage after BMT, 8.5 +/- 4.9% during the period 3-6 months after BMT and 7.0 +/- 3.0% >6 months after BMT; P < 0.05). However CD158b expression on CD3(+) T cells increased 3 months after allo-BMT (1.1 +/- 1.1% before BMT vs. 5.1 +/- 7.7% during the period 3-6 months after BMT and 3.0 +/- 2.4% >6 months after BMT, P < 0.05). The highest percentages of CD158 expression in patients without chronic GVHD (cGVHD) and those with cGVHD were compared. The percentage of CD158b(+)/CD3(+) cells and. also that of CD158b(+)/CD8(+) cells were significantly increased in patients with cGVHD compared with these in patients without cGVHD (2.6 +/- 2.0% vs. 8.0 +/- 11.2% and 2.3 +/- 1.5% vs. 8.3 +/- 11.7% respectively; P < 0.05). The exact clinical relevance of these CD158b-expressing cells is not clear. However there is an interesting possibility that CD158b-expressing cells play some role in the regulation of GVHD after allo-BMT.