Deficiency in B Cell Maturation Antigen reveals sex differences in Experimental Autoimmune Encephalomyelitis

Abstract

Abstract Multiple sclerosis (MS) is immune mediated demyelinating disease of the central nervous system (CNS) leading to neuronal damage. The disease is heterogeneous with respect to onset and clinical course, being more prevalent in women then in men with a ratio of 3:1. Further sex differences have been observed with males having a more severe and debilitating disease course compared to females. The complex interplay of immune cells, sex hormones or genetic differences could be contributing to these clinical phenomena, which remains to be elucidated. In experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, several reports have demonstrated no sex differences in disease onset or severity in C57BL/6 mice. Herein we report that deficiency in B Cell Maturation Antigen (BCMA) in C57BL/6 mice reveals a sex difference in EAE. BCMA plays a prominent role in B cell function, however the role BCMA plays in MS and EAE is unknown. Our initial goal of this project was to determine the impact BCMA deficiency has on EAE. In doing so we confirmed that EAE disease was not different in males and females from BCMA+/+mice. Strikingly in the BCMA−/− mice, there was a significant increase in EAE disease severity in males compared to females. The increased EAE in the BCMA−/− male mice was associated with increased demyelination and infiltration of inflammatory T cells and macrophages into CNS. Also, we observed decreased splenic transitional B cells in male BCMA−/− mice compared to females. Castration of mice significantly reduces EAE in BCMA−/− mice as compared to sham controls. Altogether, our data demonstrate that male hormones exacerbates EAE in BCMA−/− mice by augmenting inflammatory responses compared to females leading to increased neuro-inflammation.