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 in this case the quadratic form is called positive definite (all 1) or negative definite (all −1). If none of the terms are 0, then the form is called ; this includes positive definite, negative definite, and indefinite (a mix of 1 and −1); equivalently, a nondegenerate quadratic form is one whose associated symmetric form is a nondegenerate "bilinear" form. A real vector space with an indefinite nondegenerate quadratic form of index (denoting "p" 1s and "q" −1s) is often denoted as R particularly in the physical theory of spacetime. The discriminant of a quadratic form, concretely the class of