Mixed lymphocyte reaction supernatants exert varied effects upon gingival fibroblasts in vitro.

Supernatants from mixed lymphocyte cultures (MLRs) were tested for modulation of gingival fibroblast growth by both dye and 3H-thymidine uptake assays. Significant levels of inhibition of growth were observed with both assays with 24 and 72 hr MLR supernatants, but stimulation of growth was seen to occur, consistently, with 48 and 96 hr MLR supernatants as assessed by the dye uptake method. Fractionation of 24 hr supernatants by gel-filtration, on Ultrogel ACA 54 yielded fractions with enhanced growth inhibitory activity. The MLR supernatants would appear to contain mediators with opposing growth effects at different times during the culture.