Vitamin D supplementation modulates Th2 immune response by inducing T regulatory cells in allergic conjunctivitis

Abstract

Abstract Allergic conjunctivitis (AC) is one of the most common diseases encountered in eye clinics. Recently, Vitamin D deficiency has been shown to be associated with allergic AC. This present study was designed to evaluate the efficacy of vitamin D to suppress ovalbumin (OVA)-sensitized AC in a murine model. BALB/c mice were sensitized with OVA and aluminum hydroxide. Two weeks later, mice were challenged by OVA eyedrops for 12 days with intraperitoneal injection of vehicle or 1,25(OH)2D3. We evaluated clinical signs, the infiltration of inflammatory cells, regulatory T cells (Treg), serum IgE, and Th2 cytokines through flow cytometry and ELISA. In addition, to evaluate inhibitory function of Treg cells, anti–CD25 blocking antibody or isotype control antibody was injected intravenously during topical OVA challenge. AC development and conjunctival infiltration of eosinophils and mast cells were significantly impaired with 1,25(OH)2D3 treatment. In addition, 1,25(OH)2D3 suppressed production of OVA-specific IgE in serum and Th2 cytokines in vitro T cell assays, such as IL-4 and IL-13, compared to vehicle group. Interestingly, 1,25(OH)2D3 led to increase Treg cells population in draining LNs and suppressive levels of clinical signs and inflammatory cells infiltration into conjunctivae were reversed by depleting Treg cells. Our results suggest that vitamin D supplement alleviate allergic conjunctivitis, indicated by suppressing Th2 response in draining LNs and inflammatory cells infiltration into conjunctiva through increasing population of Treg cells in draining LNs. Therefore our results demonstrated the therapeutic potential of vitamin D for allergic diseases including asthma or atopic dermatitis.