Polyfunctional antibodies. Their biology and inheritance.

It seems likely that immunoglobulins have evolved from some archetypal molecule and those forms which are useful to the animal have been retained. It is this entire population of antibodies which forms the humoral immune system and in such a system, not only the properties of individual antibody combining regions, but the properties of the multiprotein system as a whole, are important for the defences of the body against pathogens. Antibody combining sites may bind a disparate set of structurally related and unrelated ligands. This multispecificity can be biologically meaningful: the same clone can be stimulated by different antigens. In this sense, cell surface immunoglobulins are multifunctional. The major biological consequence of antibody multispecificity is overlapping binding functions within subsets of the total antibody repertoire. The most significant impact of this overlap is: (1) it reduces the number of V genes necessary to code for the total number of combining sites; (2) the cross-stimulation of clones by structurally related and unrelated antigens may be instrumental in the normal maintenance of immune responsiveness and in addition, it may explain the ability to respond to unusual and less ubiquitous antigens; (3) the antigenic history of the animal may contribute to the maturation of the immune response by cross-stimulation of pre-selected clones of antigen binding cells.