A RAPID LIMITING DILUTION ASSAY FOR MEASURING FREQUENCIES OF ALLOREACTIVE, INTERLEUKIN-2-PRODUCING T-CELLS IN HUMANS

A limiting dilution analysis (LDA) has been established which measures the total numbers of alloreactive interleukin-2 (IL-2)-secreting T cells in human peripheral blood mononuclear cells (PBMC). A significant advantage over most previous LDA is that the assay may be completed in approximately 48 h since an IL-2-dependent 'indicator' cell line is used to reduce assay time. Results are reproducible and correlate with the degree of HLA class II antigenic disparity between responder and stimulator cells. Use of both PBMC and Epstein-Barr virus-transformed B lymphoblastoid cell lines (B-LCL) as stimulator cells permits estimation of the frequency of Epstein-Barr virus-specific T cells in different responder individuals. A modification of the assay may also be used to measure the frequencies of 'primed' alloreactive cells, i.e., those alloreactive cells which have previously encountered their specific stimulating alloantigen. Use of the assay in the clinical context of bone marrow and renal transplantation is discussed.