Peritoneal antigen-presenting cells pulsed in vivo with myelin basic protein induce the suppression of experimental...

Suppression of Experimental Autoimmune Encephalomyelitis (EAE) can be achieved by i.p. administration of soluble myelin basic protein (MBP) in adult Wistar rats before the immunization. In the present work, we analyze the role of peritoneal antigen-presenting cells (APC) in the induction of tolerance to EAE. Peritoneal cells (PC) pulsed in vivo with MBP were obtained from rats that had been intraperitoneally injected 2 h previously with soluble MBP (MBP-PC) and then inoculated in recipient rats before the induction of EAE. Our findings show that the i.p. treatment of the animals with MBP-PC before the immunization was able to diminish the incidence and severity of the disease, reduce the histological alterations, abrogate the proliferative response against MBP and change the pattern of the humoral response to MBP. Moreover, when spleen mononuclear cells (MNC) from tolerant animals were cultured together with spleen MNC from sick animals, a dose-dependent inhibition of the proliferative response was observed, arguing for the presence of a regulatory cell population in the tolerant animals. It is also demonstrated that the MBP-PC are activated and their capability of inducing suppression of EAE is highly associated with the enhanced expression of MHC class II IA molecule. Our results show that peritoneal cells pulsed in vivo with MBP are able to induce tolerance and suggest that the up-regulation of MHC class II on MBP-PC is a necessary event for tolerance induction in our model.