5D). To address whether compensation by the upregulated HRs in H1H2RKO and H3H4RKO CD4+ T cells affects the expression of HDC or the production of HA, anti-CD3, and soluble anti-CD28 mAb stimulated CD4+ T cells

were analyzed for HDC expression (Fig. 5E) by qRT-PCR and screened for HA production by enzyme immunoassay (EIA) (Fig. 5F) at 24, 48, and 72 h. Surprisingly, we did not detect a significant strain effect or (strain × time) interaction for HA production or HDC expression. These Small molecule library cell assay data therefore do not support the existence of a compensatory loop with respect to HA production and HDC expression by H1H2RKO and H3H4RKO CD4+ T cells. However, the HR expression studies clearly indicate that disease severity in H1H2RKO and H3H4RKO mice is associated with compensatory upregulation of the corresponding receptors. Here, we have assessed the overall contribution to EAE susceptibility imposed by H1R and H2R (couple via stimulatory G proteins) and the H3R and H4R (couple via inhibitory

G proteins). The results of our study demonstrate that H3H4RKO mice develop a significantly more severe mTOR inhibitor clinical disease course compared with B6 and H1H2RKO mice in association with greater pathology in the brain but not the spinal cord. In contrast, despite a significant difference in the severity of the clinical disease courses between B6 and H1H2RKO, a significant difference in pathology was not detected in either the brain or spinal cord, suggesting as in H3RKO mice [[18]], H1R and/or H2R may also play a significant role in central functions related to the severity of clinical signs. Increased susceptibility to EAE in H3H4RKO mice is associated with significantly higher production of IFN-γ and IL-17 in MOG35–55 specific ex vivo recall assays. In contrast, H1H2RKO mice exhibit decreased susceptibility to EAE and decreased BBB permeability. We have also shown that CD4+ T cells from H1H2RKO mice, upon in vitro activation, have an intrinsic immune deviation toward the Th2 phenotype, while activated T cells from H3H4RKO mice have an intrinsic PTK6 immune bias toward Th1 type cells. The results of our current study

indicate that HA signaling through H1R and H2R augments EAE susceptibility by influencing antigen-specific T-cell effector responses, immune deviation, and BBB permeability. It is well known that HA and HRs modulate the innate and adaptive immune systems [[4]]. Previously, we have shown that H1RKO mice develop less severe EAE that was associated with an immune deviation of the CD4+ T-cell population from an encephalitogenic Th1 response to a protective Th2 response [[27, 31]]. In addition, mice deficient for H2R are significantly less susceptible to acute early phase EAE and T cells from immunized H2RKO mice exhibit blunted Th1 effector cell responses [[32]]. Similar to H1R, HA acting through H2R determines T-cell effector functions and their polarization.