The invention describes assays for determining the potency of a test lot of glatiramer acetate (GA) by quantitating and comparing the levels of mRNA response biomarkers produced in mouse T-cells in response to stimulation with the test lot or a reference standard lot of GA, wherein the T-cells are obtained from mice immunized with the test lot or the reference standard lot of GA. Methods for identifying mRNA response biomarkers useful in the assays of the invention also are described.