S1PR3 and pemphigus foliaceus: To investigate the role of S1pr3 in macrophages in the pathogenesis of PF, a myeloid-specific S1pr3 knockout mouse model (the LysM-Cre+/S1pr3flox/flox mice, defined as S1pr3-CKO mice) was generated, and their littermates (the LysM-Cre−/S1pr3flox/flox mice, defined as S1pr3-C mice) served as controls (Fig. 3A).