Mixed leukxyte culture reactions in mouse thymus cells

Parenchymal thymus cells from several strains of normal, non-immunized mice responded to histoincompatible thymus cells with increased incorporation of ³H-thymidine in vitro. The response was most pronounced with mixtures of AKR + CBALB/c thymocytes which were mutually stimulatory, as determined by experiments in which one of the cell populations had been rendered unresponsive by irradiation. Reactivity was not restricted to cell combinations bearing major histo-incompatibilities; increases in ³H-thymidine uptake also occurred in cell mixtures with θ isoantigen differences. The culture technique described allows the assessment of the interaction of antigen with native thymocytes in a completely in vitro system.