Morphologic and functional characterization of human peripheral blood T cells expressing the T cell receptor γ/δ*

Abstract

The morphologic and functional characteristics of cells freshly isolated from human peripheral blood and bearing a T cell receptor (TcR) γ/δ were analyzed. Cell preparations highly enriched for TcR γ/δ⁺ cells were obtained by treatment of E rosette‐forming lymphocytes with anti‐CD4 and anti‐CD8 monoclonal antibodies (mAb) and complement. These preparations consisted of 64–82% TcR γ/δ⁺ lymphocytes, as indicated by the sum of cells reacting with the BB3 and A13 mAb which define two distinct, nonoverlapping, TcR γ/δ⁺ cell subsets in the peripheral blood. TcR γ/δ cells were able to form conjugates with the natural killer‐sensitive K‐562 and with the natural killer‐resistant HL‐60‐R tumor cell lines. The cytochemical localization of lysosomal acid hydrolases showed that 95%–98% of the cells in the TcR γ/δ⁺ preparations had the morphologic features of granular lymphocytes. Moreover, electron microscopy analyses showed that TcR γ/δ⁺ cells had electron‐dense granules dispersed in the cytoplasm and a variety of smooth vesicles, a morphology identical to that of other CD3^‐ or CD3⁺ granular lymphocyte subsets. Freshly isolated TcR γ/δ⁺ cells were unable to lyse K‐562 and natural killer‐resistant targets, such as HL‐60‐R and P815. However, low levels of target cell lysis were observed upon triggering of the effectors by anti‐CD3 TcR mAb or by lectin. After short‐term culture with inter‐leukin 2, TcR γ/δ⁺ cells acquired a strong cytolytic activity against K‐562 and HL‐60‐R target cells in the absence of triggering stimuli, and also displayed high levels of cytolytic activity against P815 in the presence of anti‐CD3/TcR mAb.