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")
Invariant of a binary form or decimics. "Quantic" is an old name for a form of arbitrary degree. Forms in 1, 2, 3, 4, ... variables are called unary, binary, ternary, quaternary, ... forms. A form "f" is itself a covariant of degree 1 and order "n". The discriminant of a form is an invariant. The resultant of two forms is a simultaneous invariant of them. The Hessian covariant of a form is the determinant of the Hessian matrix It is a covariant of order 2"n"− 4 and degree 2. The catalecticant is an invariant of degree "n"/2+1 of a binary form of even degree