A CD2 response element which resides within the first 208BP of the interferon-γ promoter regulates its expression in lamina propria T-cells

Although interferon-γ (IFN-Η) is an important pathogenic cytokine in mucosal inflammation, little is known about the molecular mechanisms regulating expression of IFN-γ in mucosal LP T cells. LPMC have enhanced IFN-γ secretion when activated through the CD2 pathway. Coligation of CD28 leads to a synergistic effect, further enhancing IFN-γ secretion. Previous studies have identified several cis-regulatory regions and DNA binding factors which modify IFN-γ gene expression in PBMC. We have examined molecular events involved in the regulation of IFN-γ production in LPMC. Activation of LPMC through the CD2 pathway resulted in increased IFN-γ production and a paralleled upregulation of mRNA. CD28 coligation further enhanced cytokine production and mRNA levels due in part to an increase in IFN-γ mRNA stability. EMSA analysis from LPMC indicates that CD2 signaling is transmitted in part by induction of nuclear protein binding to the proximal AP-1 region of the IFN-γ promoter. No further enhancement of proteins binding to this region was detected subsequent to CD28 coligation. Functional analysis following transfection of a 2.7kb IFN-γ promoter-construct into LPMC revealed that CD2 activation resulted in marked upregulation of reporter activity. CD28 coligation however, failed to induce additional reporter gene expression. Mutational analysis identified a CD2 response element residing in the first 208bp upstream of the transcriptional start site. Moreover, the -208bp-reporter construct exhibited enhanced expression as compared to the -2.7kb promoter-construct, suggesting the presence of a CD2 response represser element upstream of -208 region. These studies represent the first reports of a CD2 responsive element within the IFN-γ promoter.