Cellular immune crossreactivity between myelin basic protein and synapsin in rats with experimental allergic encephalomyelitis

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Abstract
We previously demonstrated that antibodies against myelin basic protein (MBP) obtained from animals with experimental allergic encephalomyclitis (EAE), induced with MBP and purified by affinity chromatography, have the property to recognize a neuronal protein, synapsin Ia and Ib. To investigate whether this Crossreactivity also occurs at the cellular level, we purified spleen and lymph node mononuclear cells from rats sensitized with MBP or synapsin using polystyrene plates coated with the respective antigen. We observed that animals injected with MBP have T lymphocytes that bind both antigens. Using the same system, each purified cell population was confronted again to the studied antigens. The anti-MBP cells recognized once more epitopes of MBP and about 40% of them also recognized synapsin. On the other hand, cells that first were attached to synapsin, in the second exposure to antigens bound to MBP and synapsin in similar amounts. Double immunofluorescent labeling of the mononuclear cells isolated from animals injected with bovine myelin or MBP showed that the same lymphocyte was able to recognize MBP as well as synapsin. In both experimental systems the quantitative results were similar indicating that in bovine myelin- or MBP-sensitized animals practically all the cells that recognize synapsin are anti-MBP cells, and of the total cells raised against MBP, around 40% of them show this Crossreactivity. On the contrary, animals injected with synapsin have cells that bind to this protein but not to MBP indicating that the described Crossreactivity, as observed at humoral level, is only in one way. These results suggest that the lymphocytes sensitized against MBP that also recognize synapsin could be of relevance in the pathogenesis of EAE, since neuronal structures arc affected by the immunological response to MBP.