The injection of mannan into mice can result in the development of
psoriasis (Ps) and psoriatic arthritis (PsA), whereas co-injection with
antibodies toward collagen type II leads to a chronic rheumatoid-like
arthritis. The critical event in all these diseases is mannan-mediated
activation of macrophages, causing more severe disease if the
macrophages are deficient in neutrophil cytosolic factor 1 (Ncf1), i.e.,
lack the capacity to make a reactive oxygen species (ROS) burst. In
this study, we investigated the role of one of the receptors binding
mannan; the macrophage mannose receptor (MR, CD206). MR is a C-type
lectin present on myeloid cells and lymphatics. We found that mice
deficient in MR expression had more severe mannan-induced Ps, PsA as
well as rheumatoid-like arthritis. Interestingly, the MR-mediated
protection was partly lost in Ncf1 mutated mice and was
associated with an type 2 macrophage expansion. In conclusion, these
results show that MR protects against a pathogenic inflammatory
macrophage response induced by mannan and is associated with induction
of ROS.