Human T cells expressing the γ/δ T-cell receptor (TcR-1): C(γ)1- and C(γ)2-encoded forms of the receptor correlate with distinctive morphology, cytoskeletal organization, and growth characteristics

Abstract

BB3 and δ-TCS1 monoclonal antibodies identify two distinct nonoverlapping populations of T-cell receptor (TcR) γ/δ (TcR-1)-positive cells, which express a disulfide-linked and a nondisulfide-linked form of TcR, respectively. BB3+ cells represented the majority of circulating TcR-1+ cells, but they were virtually undetectable in the thymus. On the other hand, δ-TCS1+ cells were largely predominant among TcR-1+ thymocytes but represented a minority in peripheral blood (PB). Similar distributions were observed by clonal analysis of thymocytes or PB TcR-1+ populations. The use of joining region (J)-specific probes indicated that BB3+ and δ-TCS1+ clones displayed different patterns of J rearrangement. Thus, the disulfide-linked form of TcR-1 (BB3+ clones) was associated with the expression of J segments upstream to the C(γ)1 gene segment, whereas the nondisulfide-linked form (δ-TCS1+ clones) was associated with the expression of J segments upstream to C(γ)2. δ-TCS1+ clones, in most instances, exhibited a growth pattern different from that of BB3+ or conventional TcR α/β+ clones as they adhered promptly to surfaces, spread, and emitted long filopodia ending with adhesion plaques. Ultrastructural analyses showed, exclusively in δ-TCS1+ cells, nuclear deformations, uropod formation, and abundant cytoskeletal structures. In addition, immunofluorescence studies of this subset of TcR-1+ cells revealed the presence of abundant microtubules, intermediate filaments, and submembranous microfilaments. Thus, our findings suggest that δ-TCS1+ cells are capable of active motility.