Identification of T-cell epitopes of autoantigens using recombinant proteins; studies on experimental autoimmune myasthenia gravis.

In the Lewis rat, T-cell lines from animals immunized with native or denatured Torpedo nAChR recognize the Torpedo-derived recombinant protein T alpha X1 omega (alpha-2-200) but not the equivalent mouse- or chick-derived recombinant proteins X4 omega or C alpha X1 omega (alpha 6-216 and alpha 35-216, respectively). T-cell lines derived from animals immunized with T alpha X1 omega, X4 omega or C alpha X1 omega are specific for the homologous protein. This lack of cross-species reactivity suggests caution in the use of Torpedo nAChR-selected lines generated from human patients. Proteolysis and fractionation of the products by reverse-phase HPLC was effective in localization of a T-cell epitope of X4 omega, a mouse-derived recombinant protein. With Lewis rats, the major epitope of T alpha X1 omega is alpha 97-112. However, the major epitope of the mouse-derived protein, X4 omega, as determined by proteolytic digestion and fractionation of the products by reverse-phase HPLC, is alpha 14-22. This shift in T-cell epitope between closely related proteins may result from the conservation of sequence of alpha 97-112 between mammalian species.