The CD4⁺ T cell model of action by glatiramer acetate (GA). GA induces strong MHC class II restricted proliferative responses by T cells. Daily injections of GA induces a moderate loss of responsiveness to the antigen accompanied by a shift to a more Th2 type of CD4⁺ T cell. The surviving GA-reactive T cells show a greater degree of degeneracy, as measured by cross-reactive responses to combinatorial peptide libraries. Highly cross-reactive Th2 cells with degenerate T cell receptors migrate to the site CNS, recognize self antigens as weak agonists or “altered peptide ligands”. In response, they begin to secrete Th2/Th3 cytokines, and suppress inflammation by the mechanism of bystander suppression.