Immunoglobulin A only weakly. IgA exists in two isotypes, IgA1 and IgA2. They are both heavily glycosylated proteins. While IgA1 predominates in serum (~80%), IgA2 percentages are higher in secretions than in serum (~35% in secretions); the ratio of IgA1 and IgA2 secreting cells varies in the different lymphoid tissues of the human body: Both IgA1 and IgA2 have been found in external secretions like colostrum, maternal milk, tears and saliva, where IgA2 is more prominent than in the blood. Polysaccharide antigens tend to induce more IgA2 than protein antigens. Both IgA1 and IgA2 can be in membrane-bound form. ("see B-cell receptor")
Prenex normal form Prenex normal form A formula of the predicate calculus is in prenex normal form if it is written as a string of quantifiers and bound variables, called the prefix, followed by a quantifier-free part, called the matrix. Every formula in classical logic is equivalent to a formula in prenex normal form. For example, if formula_1, formula_2, and formula_3 are quantifier-free formulas with the free variables shown then is in prenex normal form with matrix formula_5, while is logically equivalent but not in prenex normal form. Every first-order formula is logically equivalent (in classical logic) to some formula in prenex normal