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")
Sesquilinear form basis of , a sesquilinear form is represented by a matrix , by the column vector , and by the column vector : The components of are given by . A complex Hermitian form (also called a symmetric sesquilinear form), is a sesquilinear form such that The standard Hermitian form on is given (again, using the "physics" convention of linearity in the second and conjugate linearity in the first variable) by More generally, the inner product on any complex Hilbert space is a Hermitian form. A vector space with a Hermitian form is called a Hermitian space. The matrix representation