Co-Signalling Molecules (B7 homologs) are Expressed by Human Keratinocytes

RATIONALE: Co-signalling molecules are cell-surface proteins that regulate qualitative and quantitative aspects of T cell responses to antigen. Keratinocytes (KC) express receptors recognized for their role in the APC-T cell synapse, such as MHC Class II and other co-signalling molecules (i.e. CD40, B7-H1, CD58, ICAM-1). The purpose of this study was to investigate the expression of several new B7 family members (B7-DC, B7-H1, B7-H2 and B7-H4) on human KC. We also evaluated the effect of stimulation with synthetic dsRNA or inflammatory cytokines; to determinate whether signaling through innate or adaptive pathways affect B7 homolog expression.METHODS: Primary human KC isolated from foreskin or from suction blisters of adult donors, were cultured with media alone, cytokines (IFNγ 100 ng/ml, TNFα 50 ng/ml, IL-4 50 ng/ml) or dsRNA (poly I:C, 25 μg/ml) for 24 and 48h. The gene expression of B7 homologs was determined by real-time PCR. Protein expression was assessed by FACS or immunofluorescence staining of KC cultures or skin sections from skin biopsies of healthy donors.RESULTS: We report that primary human KCs isolated from fetal and adult tissues constitutively express B7-H1, B7-DC, B7-H2 and B7-H4 both in vitro and in vivo. B7-H1, B7-DC and B7-H4 surface expression was up-regulated by IFN-γ. IL-4 and TNFα had no effect expression of B7 homologs. dsRNA stimulation induced B7-H1 and B7DC gene expression on KC.CONCLUSIONS: These results suggest that the expression of B7 molecules on KCs may determine the balance of immunogenic vs tolerogenic responses, as well as Th1 vs Th2 polarization in inflammatory skin diseases. RATIONALE: Co-signalling molecules are cell-surface proteins that regulate qualitative and quantitative aspects of T cell responses to antigen. Keratinocytes (KC) express receptors recognized for their role in the APC-T cell synapse, such as MHC Class II and other co-signalling molecules (i.e. CD40, B7-H1, CD58, ICAM-1). The purpose of this study was to investigate the expression of several new B7 family members (B7-DC, B7-H1, B7-H2 and B7-H4) on human KC. We also evaluated the effect of stimulation with synthetic dsRNA or inflammatory cytokines; to determinate whether signaling through innate or adaptive pathways affect B7 homolog expression. METHODS: Primary human KC isolated from foreskin or from suction blisters of adult donors, were cultured with media alone, cytokines (IFNγ 100 ng/ml, TNFα 50 ng/ml, IL-4 50 ng/ml) or dsRNA (poly I:C, 25 μg/ml) for 24 and 48h. The gene expression of B7 homologs was determined by real-time PCR. Protein expression was assessed by FACS or immunofluorescence staining of KC cultures or skin sections from skin biopsies of healthy donors. RESULTS: We report that primary human KCs isolated from fetal and adult tissues constitutively express B7-H1, B7-DC, B7-H2 and B7-H4 both in vitro and in vivo. B7-H1, B7-DC and B7-H4 surface expression was up-regulated by IFN-γ. IL-4 and TNFα had no effect expression of B7 homologs. dsRNA stimulation induced B7-H1 and B7DC gene expression on KC. CONCLUSIONS: These results suggest that the expression of B7 molecules on KCs may determine the balance of immunogenic vs tolerogenic responses, as well as Th1 vs Th2 polarization in inflammatory skin diseases.