Provided herein are methods and kits for assaying antigen-specific T cell responses, such as rare autoantigen-specific T cell responses, by measuring a level of IP-10 in a sample from a subject having or suspected of having an autoimmune disease, an allergy, an infectious disease or condition, or an adverse immune condition caused by administration of an isolated, recombinant or synthetic protein or peptide. Also provided herein are methods and kits for assaying a T cell response to an antigen peptide, such as an islet autoantigen peptide, such as measuring a T cell response to at least one antigen peptide, such as an islet autoantigen peptide, in a sample from a subject, such as one having or suspected of having Type 1 Diabetes (TID), Celiac disease or both.
