Characterization of γ:δ T-Cell Receptor Expressed on Peripheral Blood Lymphocytes After Allogeneic Bone Marrow Transplantation

Two kinds of T-cell antigen receptor (TCRs) α:β and γ:δ, have so far been identified as independently expressed on the cell surface of distinct subsets of T cells in association with the CD3 (T3) complex (1,3). The surface expression of these TCR was systematically analyzed in peripheral lymphocytes (PBL) from 27 patients (pts) having received allogeneic bone marrow transplantation for leukemia. A predominant emergence of circulating CD3+ lymphocytes— 40% of PBL—lacking α:β heterodimer was demonstrated in 3 pts. In two pts, we showed that these cells expressed γ chains associated to CD3. In one pt, functional analyses indicated that this γ:δ subset representing 40% of PBL may have played a role in a profound immunodeficiency state which occurred six months after grafting. Molecular studies of γ:δ cells indicated that these circulating cells preferentially expressed a single Vγ segment of the T-cell receptor γ gene (TRG): Vγ5 for pt 1 and Vγ9 for pt 2.