Lymphotoxin, tumor necrosis factor, and gamma interferon are cytostatic for normal human keratinocytes

Abstract

The effects of crude lymphokine-enriched supernatants, purified recombinant lymphotoxin (LT), tumor necrosis factor-α (TNF), and gamma interferon (γIF) on proliferating human keratinocytes were assessed using two in vitro culture systems. Activated splenocyte supernatants inhibited keratinocyte colony growth on fibroblast feeder layers and arrested basal keratinocyte DNA synthesis within 24 h. Purified recombinant LT, TNF, and γIF inhibited cell proliferation in serum-free medium without noticeably affecting viability. Cytostasis was dose-dependent (up to 90% with LT or TNF and 99% with γIF) and was maximal within 24-36 h. Specific antibodies neutralized TNF- and γIF-mediated cytostasis. Combined treatment with LT (or TNF) and γIF increased the degree of cytostasis, particularly at low lymphokine concentrations. Maximum inhibition of DNA synthesis and the duration of exposure required for this inhibition were comparable for LT and TNF and differed for γIF. Each of these lymphokines induced cell enlargement, flattening, and vesiculation, with γIF apparently more potent in this respect than LT or TNF. Fusiform keratinocytes with diffusely distributed cytokeratin were observed after prolonged treatment with γIF alone or γIF plus either LT or TNF. Flow cytometric studies of lymphokine-treated keratinocytes indicated that LT, TNF, and γIF could enhance beta-2 microglobulin expression 1.5-fold to threefold, whereas only γIF induced class II antigens. Staining for class II and beta-2 microglobulin was reduced on cells treated with high concentrations of γIF compared with either optimally treated or untreated cells. The potential relevance of these findings to cutaneous immune defense and disease is discussed. © 1989.