FREQUENCY, SPECIFICITY, AND PHENOTYPE OF CLONALLY GROWING HUMAN ALLOREACTIVE INTERLEUKIN-2-SECRETING HELPER LYMPHOCYTE-T PRECURSORS

Limiting dilution cultures were performed to detect allospecific IL-2-secreting helper T lymphocyte precursors (HTL-p) among human peripheral blood mononuclear cells, E-rosette-purified (E+) and cell-sorter-separated CD4+/8−as well as CD4−/8+T cell subsets. Split- well cultures were set up prior to restimulation to assess the antigen specificity of the response. Frequencies of alloreactive IL-2-secreting HTL-p in fully HLA-mismatched responder/stimulator cell combinations ranged from 1/200 to 1/900 (among PBMNC), from 1/50 to 1/301 (among E+T cells), from 1/36 to 1/ 220 (among CD4+T cells), and from 1/38 to 1/450 (among CD8+T cells). Allospecificity of effector T cells was demonstrated by a strong decline of frequencies obtained after restimulation against unrelated third- party antigens. In clonal segregation analysis, the vast majority of IL-2-secreting progeny (80–90%) were exclusively specific for the original stimulating alloantigen. Finally, the allele specificity of human alloreactive HTL-p was revealed by comparing frequency estimates obtained after restimulation with partially identical stimulator/third-party antigen combinations. © 1990 by Williams & Wilkins.