People with a deficiency in the AIRE protein suffer from a broad spectrum autoimmune disease that involves immune attack against a diverse set of body tissues and organs. Which statement below most accurately provides a mechanistic explanation of this disease? a. These patients have a defect in class II MHC expression which results in an inability to positively select for Th cells. b. These patients do not have a thymus gland and thus are unable to create T lymphocytes. c. These patients suffer from a defect in negative selection of immature B cells. d. These patients suffer from a defect in negative selection of thymocytes.