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")
Modular form The situation with modular forms is precisely analogous. Modular forms can also be profitably approached from this geometric direction, as sections of line bundles on the moduli space of elliptic curves. If "f" is holomorphic at the cusp (has no pole at "q" = 0), it is called an entire modular form. If "f" is meromorphic but not holomorphic at the cusp, it is called a non-entire modular form. For example, the j-invariant is a non-entire modular form of weight 0, and has a simple pole at i∞. Other common generalizations allow the weight "k" to not be an integer,