Persistence of T8+/HNK-1+ suppressor lymphocytes in the blood of long-term surviving patients after allogeneic bone marrow transplantation

Fifteen patients and their respective bone marrow donors were entered in this study 1 to 5 yr after allogeneic bone marrow transplantation. Peripheral blood E rosetting (T) cells were analyzed for their phenotypic characteristics as well as for their ability to regulate Ig synthesis in the in vitro PWM system. A close relationship was found between a high proportion of T8+/HNK-1+ cells and/or T8+/HLA-DR+ cells and a strong (greater than or equal to 50%) inhibition of the antibody response. It was noteworthy that even the patients without suppressor activity had high proportions of such cells when compared with normal marrow donors. Moreover, the suppression occurred irrespective of the presence or absence of chronic GVHD. Through negative selection experiments (with MAb and complement) and through immunofluorescence cell sorting, it was shown that the suppressor cells expressed the T8+, HNK-1+, HLA-DR- phenotype. They did not carry the Leu-11, NKH1A, or NKH2 determinants, which are expressed on mature functional NK cells. When examined by electron microscopy, they exhibited a morphology of resting agranular lymphocytes. The significant increase of these suppressor cells among the BMT patients was not correlated with clinical syndromes such as chronic GVHD or opportunistic viral infections, which argues against the notion of in vivo profound immunodeficiency coexisting with these cells.