H₁R expression by CD11B⁺ cells is not required for susceptibility to experimental allergic encephalomyelitis

The histamine H₁ receptor (Hrh1/H₁R) was identified as an autoimmune disease gene in experimental allergic encephalomyelitis (EAE), the principal autoimmune model of multiple sclerosis (MS). Previously, we showed that selective re-expression of H₁R by endothelial cells or T cells in H₁RKO mice significantly reduced or complemented EAE severity and cytokine responses, respectively. H₁R regulates innate immune cells, which in turn influences peripheral and central nervous system CD4⁺ T cell effector responses. Therefore, we selectively re-expressed H₁R in CD11b⁺ cells of H₁RKO mice to test the hypothesis that H₁R signaling in these cells contributes to EAE susceptibility. We demonstrate that transgenic re-expression of H₁R by H₁RKO-CD11b⁺ cells neither complements EAE susceptibility nor T cell cytokine responses highlighting the cell-specific effects of Hrh1 in the pathogenesis of EAE and MS, and the need for cell-specific targeting in optimizing therapeutic interventions based on such genes.