Induction of fibroblast proliferation by human mononuclear leukocyte‐derived proteins

Human peripheral blood mononuclear leukocytes stimulated by T cell antigen or mitogen release soluble factors that induce mitogenesis of dermal fibroblasts in vitro. Fractionation of supernatants from antigen-stimulated mononuclear leukocyte cultures by Sephadex G-100 yielded 2 major peaks of fibroblast proliferation activity (approximately 60,000 and approximately 16,000 MW). Both proliferation factors are heat stable (56 degrees C for 45 minutes) proteins. These data show that mononuclear leukocytes, under appropriate conditions, can release soluble mediators that can stimulate fibroblast proliferation; such leukocytes may also play a role in expanding fibroblast populations adjacent to certain cell-mediated immune reactions in vivo.