Gamma delta T-cell receptor repertoire in human peripheral blood and thymus.

T-cell clones expressing the gamma delta T-cell receptor (Tcr) were generated from peripheral blood lymphocytes (PBLs) and from a thymus sample. In the panel of ten thymus-derived clones, four gamma delta Tcr phenotypes [as defined by the reaction of monoclonal antibodies (mAbs) directed against known V gamma and V delta regions] were identified. All the clones lacked expression of the V delta 3 V region, while seven clones were V delta 1+. V delta 1 was found in combination with V gamma 9 or with undefined V gamma V regions. In addition, two other gamma delta Tcr phenotypes were identified on these clones: V gamma 9+V delta 1-V delta 3- and V gamma 9-V delta 1-V delta 3-. One of the clones expressed CD4 and another was CD8-positive. The remaining clones were CD4-CD8-. In the panel of 76 PBL-derived, gamma delta Tcr-bearing clones, five gamma delta Tcr phenotypes could be identified. In contrast to the thymus-derived clones, 30% of the clones were V delta 3+ whereas V delta 1 was expressed by a minority of the clones only. One clone was CD4-positive and approximately 30% of the clones were CD8-positive. Four of the five mAb-defined gamma delta Tcr phenotypes could be identified on both thymus and PBL-derived T-cell clones. However, biochemical analysis of the Tcrs demonstrates differences in the usage of C gamma 1- and C gamma 2-encoded gamma chains by T cells derived from the thymus and PBLs. The results therefore indicate that, at the clonal level, similarities and differences exist between the gamma delta Tcr repertoires expressed in the thymus and by PBLs. Furthermore, they indicate that combinatorial gamma delta Tcr heterogeneity is larger than has so far been described. The receptor diversity, combined with the potential of gamma delta Tcr+ cells to express CD4 or CD8, indicates that these cells are a heterogeneous population that might mediate a number of immune functions.