The C-type lectin receptor Clec1A plays an important role in the development of experimental autoimmune encephalomyelitis by enhancing antigen presenting ability of dendritic cells and inducing inflammatory cytokine IL-17

Clec1A, a member of C-type lectin receptor family, has a carbohydrate recognition domain in its extracellular region, but no known signaling motif in the cytoplasmic domain. Clec1a is highly expressed in endothelial cells and weakly in dendritic cells. Although this molecule was reported to play an important role in the host defense against Aspergillus fumigatus by recognizing 1,8-dihydroxynaphthalene-melanin on the fungal surface, the roles of this molecule in un-infected animals remain to be elucidated. In this study, we found that Clec1a(−/−) mice develop milder symptoms upon induction of experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. The maximum disease score was significantly lower, and demyelination and inflammation of the spinal cord were much milder in Clec1a(−/−) mice compared to wild-type mice. No abnormality was detected in the immune cell composition in the draining lymph nodes and spleen on day 10 and 16 after EAE induction. Recall memory T cell proliferation after restimulation with myelin oligodendrocyte glycoprotein peptide (MOG(35–55)) in vitro was decreased in Clec1a(−/−) mice, and antigen presenting ability of Clec1a(−/−) dendritic cells was impaired. Interestingly, RNA-Seq and RT-qPCR analyses clearly showed that the expression of inflammatory cytokines including Il17a, Il6 and Il1b was greatly decreased in Clec1a(−/−) mice after induction of EAE, suggesting that this reduced cytokine production is responsible for the amelioration of EAE in Clec1a(−/−) mice. These observations suggest a novel function of Clec1A in the immune system.