Lymphokine stimulation of collagen accumulation

Lymphokine-rich supernates from normal human peripheral blood mononuclear cells, stimulated by the mitogen phytohemagglutinin, have been shown to cause enhanced collagen accumulation by human embryonic lung fibroblasts (WI-38), as measured by hydroxyproline content of fibroblast monolayers, [14C] proline incorporation into soluble collagen and collagenase release of radioactivity in supernates and monolayers of cultures incubated with [14C] proline. This fibroblast-stimulating activity, demonstrable by suitable dilutions of the supernates, coexisted with a number of other lymphokine activities such as lymphotoxin, proliferation inhibitory factor, and cloning inhibitory factor, which tend to reduce the numbers of function of fibroblasts. The increased content of collagen appeared to be the product of selected surviving and responding fibroblasts. The factor causing this increased collagen accumulation was nondialyzable and stable at -70 degrees C. It represents the first described lymphoid cell-derived activity capable of enhancing collagen accumulation. Fibroblast-stimulating activity may be implicated in the abnormal fibrosis seen in association with chronic inflammation in a variety of disease states. It may have special relevance to progressive systemic sclerosis.