Human keratinocyte-lymphocyte reactions in vitro.

To extend our observation that recombinant gamma interferon (r-IFN-gamma) induces the synthesis and expression of HLA-DR antigen we have investigated 2 major areas including the modulation of r-IFN-gamma-induced HLA-DR expression and the possible immunologic consequences of keratinocyte HLA-DR expression in vitro. The induction of keratinocyte HLA-DR expression was greater for continuous compared with pulse dosage (0.5-24 h) of r-IFN-gamma and was markedly decreased after trypsinization of attached monolayers into single cell suspensions. The r-IFN-gamma caused induction of HLA-DR and this was not influenced by either pretreatment with irradiation, PGE2, or indomethacin. Both HLA-DR+ and HLA-DR- cultured keratinocytes induced RNA synthesis and gamma interferon production by allogeneic peripheral blood mononuclear leukocytes (PBMLs) indicating mononuclear cell activation. However, this activation was not followed by significant mitogenesis and only slightly increased levels of [3H]thymidine incorporation (maximal = 5800 cpm) by the PBMLs was observed. Cultured keratinocytes apparently inhibit both lectin-driven and mixed-lymphocyte reactions by producing a soluble mediator which is not dialyzable, or inhibited by pretreatment with indomethacin or anti-alpha, -beta, -gamma interferon antibodies. These results suggest that lymphocyte-keratinocyte reactions in vitro are complex and may be mediated by a variety of cytokines, lymphokines, and prostaglandins.