Mucosa-specific targets for regulation of IFN-gamma expression: Lamina propria T cells use different cis-elements than peripheral blood T cells to regulate transactivation of IFN-gamma expression

Activation of lamina propria (LP)T cells via the CD2 pathway enhances IFN-g amma (IFN-gamma) secretion with further enhancement after CD28 coligation, The molecular mechanisms regulating IFN-gamma expression in LP T cells rema in unknown. Previous studies in PBL and T cell lines identified cis- and tr ans-regulatory elements in TCR-mediated expression of IFN-gamma, This study examines CD2 and PMA/ionophore-responsive IFN-gamma promoter elements, Act ivation of LPMC via CD2-induced IFN-gamma secretion and a parallel up-regul ation of mRNA expression. CD28 coligation enhanced mRNA stability without u p-regulating transcription as measured by nuclear run-on. Transfection of a --2.7-kb IFN-gamma promoter-reporter construct into PBL and LP mononuclear cells (LPMC) revealed significant promoter activity after CD2 activation, with additional transactivation after CD2/CD28 costimulation in PBL, but no t in LPMC. Functional analysis using truncated promoter fragments identifie d distinct cis-regulatory regions selectively transactivating LFN-gamma exp ression in PBL compared with LPMC. In PBL, CD2 activation elements reside w ithin the -108- to +64-bp region, However, in LPMC the upstream region betw een --204 and --108 bp was essential. Transfection of the proximal and dist al AP-l-binding elements, as well as TRE/AP-1 constructs, revealed function al activation of AP-1 subsequent to CD2 signaling, with activation critical in PBL but diminished in LPMC. Electromobility shift analysis using oligon ucleotides encompassing the proximal, distal, and BED/AP-1-hinding regions failed to demonstrate selective transactivation after CD2 signaling of LPMC , This report provides evidence that activation of LPMC results in transact ivation of multiple promoter elements regulating LFN-gamma expression disti nct from those in PBL.