Phenotypic and functional characterization of human T cell clones

The capacity of human peripheral blood-derived T cell clones to carry out a variety of functions was examined. T cell clones were generated by stimulating individual peripheral blood T cells with PHA by a procedure that yielded a growing clone from a mean of >92% of the cultured cells. A total of 65 T cell clones (44 CD4⁺ and 21 CD8⁺) generated from two individual donors were examined for their functional capabilities. All T cell clones examined secreted IL-2, IFN-γ, and lymphotoxin/tumor necrosis factor like activity when stimulated with immobilized mAb to the CD3 complex (64.1). When 54 additional T cell clones from a third donor were analyzed, all were found to produce IL-2. Upon activation with immobilized 64.1, all CD4⁺ clones and 91% of the CD8⁺ clones induced the generation of Ig-secreting cells from purified B cells. The CD8⁺ clones that did not serve as Th cells alone were able to augment the capacity of fresh CD4⁺ cells to generate Ig-secreting cells. Each of these clones was also found to effect MHC-unrestricted cytotoxicity upon activation with immobilized 64.1 The CD8⁺ clones were somewhat more effective killers than CD4⁺ clones, although there was considerable overlap. A total of 18 clones was analyzed for TCR β-chain gene rearrangement. Of the clones exhibiting rearrangements of the β-chain gene, 94% were found to have a single rearrangement pattern. Finally, the detailed phenotype of 15 (11 CD4⁺ and 4 CD8⁺) of these clones was examined. Variable numbers of cells of each of the clones expressed Ag identified by mAb 4B4 (CD29), Leu 8, Leu 15 (CD11b), and NKH1. Moreover, cells of 6 of 11 CD4⁺ clones and 4 of 4 CD8⁺ clones also expressed CD45R in addition to CD29; expression of CD45R and CD29 varied with the activation status of the clone. The current data demonstrate that nearly all of the T cell clones were able to accomplish each of the functions examined regardless of the surface phenotype. Inasmuch as the clones were generated using a technique that expanded more than 92% of the circulating T cells, the data imply that the progeny of the vast majority of T cells may have the inherent capacity to exert a wide array of functional activities.