Differentiation of Cytotoxic T Lymphocytes Enhanced by T Cell Factors Produced during Mixed Lymphocyte Interactions
Cooperation between subpopulations of T lymphocytes was demonstrated in graft-vs.-host (1) and in recruitment (2) reactions in vivo and in the mixed lymphocyte culture (MLC) in vitro (3–5). It was hypothesized that such cooperation is mediated by soluble factor(s) generated during allogeneic mixed lymphocyte interactions (4–6). We found (7) that the addition of allogeneic stimulator lymphocytes to the sensitization phase of an in vitro T cell mediated anti-fibroblast reaction (AFR) enhanced sensitization as evidenced by an increased cytolytic capacity of the sensitized T lymphocytes. In addition we found that the same effect could also be produced by T-cell soluble factors generated in the MLC (8). In the present study we investigated at what stage of the sensitization phase the MLC active factor(s) exert their effect, and whether the factors can be produced by thymocytes.
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