Thymic hormonal effect on human peripheral blood lymphocytes in vitro. III. Conditions for mixed lymphocyte-tumor culture assay

Conditions for the reproducible measurement of thymic hormonal effect on the functional activity of human peripheral blood lymphocytes (PBL) were determined using a mixed lymphocyte-tumor culture assay. Three thymic hormonal preparations (thymopoietin, thymic humoral factor and TP-1) were tested by this assay and found to have a significant enhancing effect on the blastogenic response. Essential for the demonstration of the hormonal effect was the selection of suboptimal stimulation conditions, with the appropriate cell lines, including the number of stimulating cells and the time in culture. The most reproducible results were achieved when 1 × 10⁵ PBL were co-cultured for 4 days with 1 × 10⁴ mitomycin-C treated Raji lymphoma cells, after 1 h preincubation with one of the thymic preparations. However, strong enhancing effects of the thymic preparations could also be demonstrated with other tumor cell lines, especially IgR₃ melanoma cells.