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 of a complex Hermitian form is a Hermitian matrix. A complex Hermitian form applied to a single vector is always real. One can show that a complex sesquilinear form is Hermitian iff the associated quadratic form is real for all . A complex skew-Hermitian form (also called an antisymmetric sesquilinear form), is a complex sesquilinear form such that Every complex skew-Hermitian form can be written as times a Hermitian form. The matrix representation of a complex skew-Hermitian form is a skew-Hermitian matrix. A complex skew-Hermitian form applied to a single vector is always pure imaginary. This section applies unchanged when