CD28^-CD57⁺ T cells predominate in CD8 responses to glatiramer acetate

Human T cells adopt a CD28^-CD57⁺ phenotype in chronic viral infections and this has been hypothesized to result from continuous stimulation, however this phenotype may be due to direct viral effects on T cells. Employing MS patients before and after chronic in vivo administration of the antigen glatiramer acetate (GA) we examine this hypothesis. Pre-treatment glatiramer acetate-specific CD8 T cells were CD57^-Perforin^-. This changed to a predominantly CD28^-CD57⁺Perforin⁺ response after administration of this drug. This phenotype was only observed after chronic stimulation and not in a recall response to mumps. The relevance to GA's mechanism of action is discussed.