49. Which of the following most accurately describes a mechanism leading to autoimmune disease? (A) Clonal expansion of autoreactive T cells in the absence of regulatory T cell inhibition. (B) Failure of macrophages to recognize bacterial pathogens, leading to autoantibody production. (C) Excessive activation of the complement system in response to allergens. (D) Increased function of regulatory T cells that suppress immune responses to self-antigens. (E) Overproduction of IgA antibodies that neutralize self-antigens.