The influence of pregnancy on development and course of chronic relapsing experimental autoimmune encephalomyelitis in rats: implications for multiple sclerosis.

Multiple sclerosis is a chronic, autoimmune disease of the central nervous system, which mainly affects young women during a reproductive period of life. Since, its symptoms might be significantly affected by pregnancy, in this study we investigated the development and kinetics of disease in the model of chronic relapsing experimental autoimmune encephalomyelitis (CR-EAE), induced in genetically susceptible Dark Agouti (DA) strain of rats. They were sensitized with bovine brain white matter homogenate (BBH) in complete Freund's adjuvant during the first, second or third week of pregnancy, and the disease scores were compared between treatment groups, and identically treated nongravid females. Additionally, the susceptibility to the induction of EAE was tested in offspring of mothers that during the pregnancy were sensitized with BBH. The data have shown that pregnancy does not block the induction of EAE, but that it significantly changes the course of diseases, depending on time of immunization. In rats sensitized during the first week of gestation the onset of the clinical signs was delayed, but after the delivery the intensity of disease significantly increased. Similar aggravation, with appearance of monophasic form of disease was observed in the group of rats sensitized during the third week of gestation. On the contrary, in rats sensitized during the second week of gestation the beneficial effects were observed, with later onset of attacks, and lower disease score. Furthermore, offspring of these rats after immunization with BBH developed a monophasic form of EAE of lower intensity, suggesting that some protective factors might be transferred across the placenta.