ABSTRACT
“To err is human,” and our immune system is neither more nor less frail than any other part of our body. Immune responses to invading microbial components, and other antigens in the environment, may produce effects harmful to the host. Occasionally, the immune system may even generate humoral and cell-mediated responses against our own macromolecules. As the word “pathology” designates any deleterious process within the tissues and systems of an organism, so does its derivative immunopathology designate those processes arising from immune system dysfunction, or harmful “side effects” of its physiologic function. The various immune phenomena leading to tissue injury have been called hypersensitivity. Following the system of Gell and Coombs, these reactions may be classified into five types:
Type I —Immediate hypersensitivity (anaphylaxis).
Type II —Antibody-dependent cytotoxicity.
Type III —Immune complex reactions.
Type IV —Delayed hypersensitivity.
Type V —Stimulatory reactions.
