recep'tor

[L. receiver; recipio, I receive.] 1. In Ehrlich's theory of immunity, one of the side Receptors of the ist, 2D, and 3D Orders, as i. a, the receptor; b, the combined toxin molecule with haptopnore (c) and toxophore (d) groups. 2. e, haptophore, and d, zymophore groups;/, combined food ' molecule. 3. e, haptophore (cytophile), and g, complementophile group A, complement with h, haptophore, and z, zymotoxic; groups; /, combined food molecule (after Ehrlich) chains* of the cell which combine with foreign substances this foreign substance may be something needed for the nutrition of the cell or it be a destructive toxin. When some or all the receptors of a cell are bound by toxin, the remaining receptors of that cell, or the receptors of uninjured cells, are stimulated to overproduction (see Weigert's* law); those in exce of the needs of the cell are thrown off and circulate in the blood there they seize upon any toxin present and bind it so that it is unable to attack the cell; these free receptors in the blood-plasma constitute the antitoxin. 2. Sherrington's term for one of the nerve-endings in the skin and organs of sense. r. of the first order, a r. which po e es only a haptophore group and can therefore merely bind the toxin or a food molecule, but provides no ferment for the digestion of the latter; antitoxin is a receptor of the first order, r. of the second order, a which has two groups, a haptophore group for the anchoring of the foreign molecule and a zymophore group for its digestion precipitins and agglutinins are receptors of the second order, r. of the third order, a i. which has two combining groups, a haptophore group for the anchoring of the foreign molecule and a complementophile group which binds the complement that carries the zymotoxic principle; these receptors differ from those of the second order in that the digesting principle is not a component part of the receptor but comes to it in the complement; the cytolysins (hemolysins, bacteriolysins) are cast-off receptors of the third order, ses's lle r., in Ehrlich's side-chain theory, a r. of peculiar construction which cannot be cast off to form an antibody.