Abstract The histamine H1 receptor (Hrh1/H1R) was identified as a shared autoimmune disease (SAID) gene in experimental allergic encephalomyelitis (EAE) and autoimmune orchitis, the principal AI models of multiple sclerosis (MS) and idiopathic male infertility, respectively. As a SAID gene, Hrh1/H1R can exert effects in multiple cell types including endothelial cells, T cells, and antigen presenting cells at critical check points during both the induction and effector phases of disease. In this regard, we showed that selective re-expression of H1R by endothelial cells in Hrh1-KO (H1RKO) mice significantly reduced disease severity whereas H1R expression by H1RKO T cells complemented EAE severity and cytokine responses. Given that the H1R has been reported to influence innate immune cell maturation, differentiation, chemotaxis, and cytokine production, which in turn influences CD4+ T cell effector responses, we selectively re-expressed H1R in CD11b+ myeloid cells of H1RKO mice to test the hypothesis that H1R signaling in these cells contributes to EAE susceptibility and/or T cell effector responses. We demonstrate that transgenic re-expression of H1R by H1RKO-CD11b+ cells neither complements EAE susceptibility nor T cell cytokine responses. These results further highlight the cell-specific effects that an AID gene can play in the pathogenesis of complex diseases such as EAE and MS, and the need for cell-specific targeting in optimizing therapeutic interventions based on such genes.