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")
Quadratic form is also called a quadratic form. Two "n"-dimensional quadratic spaces and are isometric if there exists an invertible linear transformation (isometry) such that The isometry classes of "n"-dimensional quadratic spaces over "K" correspond to the equivalence classes of "n"-ary quadratic forms over "K". Let "R" be a commutative ring, "M" be an "R"-module and be an "R"-bilinear form. A mapping is the "associated quadratic form" of "b", and is the "polar form" of "Q". Alternatively, a quadratic form may be characterized as follows: Two elements "v" and "w" of "V" are called orthogonal if . The kernel of a bilinear