Antigen
In immunology, antigens (Ag) are structures (aka substances) specifically bound by antibodies (Ab) or a cell surface version of Ab ~ B cell antigen receptor (BCR). The term antigen originally described a structural molecule that binds specifically to an antibody only in the form of native antigen. It was expanded later to refer to any molecule or a linear molecular fragment after processing the native antigen that can be recognized by T-cell receptor (TCR). BCR and TCR are both highly variable antigen receptors diversified by somatic V(D)J recombination. Both T cells and B cells are cellular components of adaptive immunity. The Ag abbreviation stands for an antibody generator.
Antiandrogen
Androgen synthesis inhibitors are enzyme inhibitors that prevent the biosynthesis of androgens. This process occurs mainly in the gonads and adrenal glands, but also occurs in other tissues like the prostate gland, skin, and hair follicles. These drugs include aminoglutethimide, ketoconazole, and abiraterone acetate. Aminoglutethimide inhibits cholesterol side-chain cleavage enzyme, also known as P450scc or CYP11A1, which is responsible for the conversion of cholesterol into pregnenolone and by extension the production of all steroid hormones, including the androgens. Ketoconazole and abiraterone acetate are inhibitors of the enzyme CYP17A1, also known as 17α-hydroxylase/17,20-lyase, which is responsible for the conversion of pregnane steroids into androgens, as well as the conversion of mineralocorticoids into glucocorticoids. Because these drugs all prevent the formation of glucocorticoids in addition to androgens, they must be combined with a glucocorticoid like prednisone to avoid adrenal insufficiency. A newer drug currently under development for treatment of prostate cancer, seviteronel, is selective for inhibition of the 17,20-lyase functionality of CYP17A1, and for this reason, unlike earlier drugs, does not require concomitant treatment with a glucocorticoid.