A method for measuring cell-mediated immunity to AAV-related gene therapy is provided. The method includes measuring cell-mediated immunity to adeno-associated viruses (AAV) and the transgene carried by these viruses which are being used for gene replacement therapy to treat genetic disorders. These measurements are used to a) estimate the risk of failure, b) the adequacy of immunosuppression, c) adjustment of immunosuppression d) to achieve desired suppression of the immune response, and e) to determine whether a patient about to undergo gene therapy is likely to develop and immune response to the therapy or not. The related embodiment which measures several complement or related proteins on cells is aimed at measuring the risk of TMA, its severity and its response to treatment. The present invention also provides a kit for measuring cell mediated immunity to AAV gene therapy.