[The growth-stimulating and immunomodulating activity of culture media conditioned by transformed fibroblasts from serum-free lines].

Five cell lines of transformed rodent fibroblasts capable of unlimited growth without exogenous proteins were studied. It has been demonstrated that the media conditioned by these cells (CMs), the protein preparations obtained from CMs, or the feeder cell cultures of the serum-free cell lines are mitogenic to mouse hybridoma cells as well as to primary cell cultures of the rat bone marrow. The addition of CMs proteins into mixtures of mouse splenocytes and transformed target cells resulted in stimulation or suppression of the splenocyte cytotoxicity when YAC-1 [correction of JAC-1] or K562 cell targets were used. A 18-20 h splenocyte preincubation with proteins, released by transformed rat fibroblasts of the serum-free cell line LRec-1sf, resulted in a 1.5-4-fold increase in K562 cell lysis by murine natural killer cells. By contrast, the target cell preincubation with the same proteins resulted in a 1.5-2-fold decrease in K562 cell sensitivity to cytotoxic effect of natural killer cells. Taken together our data show that the transformed rodent fibroblasts, growing without exogenous proteins, produce and release into the culture medium some growth stimulating, immunomodulating and immunoprotective factors.