Specificity spectrum and cell surface markers of mono- and multi-functional mixed leukocyte culture-derived T cell clones in man.

Abstract

AbstractAlloactivated human lymphocytes have been cloned by limiting dilution followed by expansion of clonal progeny using interleukin 2. Their differing functional specificities were analyzed in terms of reactivity in primed lymphocyte typing (PLT), cell‐mediated cytotoxicity to normal peripheral blood mononuclear cells or to cell line targets susceptible to lysis by natural killer cells, and finally, suppressive capacity in mixed leukocyte cultures. T lymphocyte clones mediating exclusively PLT, CML or suppression were isolated. In contrast, all clones with natural killer‐like activity were found to be multifunctional, in that they strongly suppressed mixed leukocyte cultures, as well as having variable, although generally weak, activity in PLT and CML. From a total of 148 clones initially screened, about half manifested PLT reactivity. Of these, 60% were restimulated exclusively by determinants associated with the HLA‐D type of the original priming cells, whereas the remainder were restimulated by a variety of different HLA‐D as well as HLA non‐D products. Similar heterogeneity of responses at the clonal level was observed among the populations active in CML. Using monoclonal antibodies, surface marker phenotyping of functionally distinct clones was undertaken in an attempt to correlate surface marker profiles with particular functions. It was found that all clones tested were mature, activated T cells (Lyt‐3+, T28+, OKT3+, HLA‐DR+, HTA1‐1, OKT6−). Many of the clones described here, whether functional in PLT CML, having natural killer‐like or suppressor cell activity, expressed putative “helper/inducer” T cell markers defined by OKT4. The putative “suppressor/cytotoxic” marker OKT8 appeared on some natural killer‐functional clones, but not on CML or suppressor cell clones. Clones with natural killer‐like function were identifiable by their additional unique expression of the antigen detected by the rat monoclonal antibody YD1/48.HLK, whereas the monoclonal antibody M522 reacted selectively with clones having natural killer or CML function, but not with those with PLT or suppressor cell function. These results show that cloned T cells with PLT, CML, natural killer or suppressor activities, derived from MLC, can act as valuable tools in the elucidation of T cell function in vitro. To this end, the correlation of defined function with analysis of cell surface markers using monoclonal antibodies will be of value in dissecting components of human immune responses and determining the functional relevance, if any, of structures detected by such antibodies.