C5a/C5aR1 mediates the IMQ-induced psoriatic skin inflammation via promoting IL-17A expression by γδ T cells in mice

Objective To explore the effects and underlying mechanism of C5a/C5aR1 pathway in mediating imiquimod (IMQ)-induced psoriatic skin inflammation by increasing IL-17A expression in γδ T cells. Methods C5aR1+/+ and C5aR1-/- mice were treated with IMQ or control Vasline cream for 6 consecutive days. The psoriatic skin inflammation was monitored. Inflammatory cells infiltration (T cells and neutrophils) and cytokines expression (IL-17A and TNF-α) were tested by immunohistochemistry (IHC). The percentages and cellular sources of IL-17A in both draining lymph nodes and skin lesions were analyzed by flow cytometry (FCM). Before IMQ application,C5aR1a peptide was injected into C5aR1+/+ mice and the psoriatic skin lesions as well as IL-17A expression were examined. Additionally, the isolated spleen lymphocytes were stimulated with C5a, IL23 or C5aR1a and then tested with FCM for the expression of IL-17A in γδ T cells. Results It was shown that C5aR1 deficiency clearly ameliorated IMQ induced psoriatic skin inflammation