IgA in blood and thoracic duct lymph: concentration and degree of polymerization.

Lymph fluid and serum samples from four mammalian species were studied forthe concentration and degree of polymerization of IgA. The results suggest that in the mouse, in the rat and in the dog circulating IgA represents only a small fraction of all IgA entering the blood stream from the lymph vessels. A majority of the input IgA of oligomeric type (13S, 11S and 9S) in these species is cleared rapidly. Monomeric IgA, and in the mouse and the dog the dimeric (9S) variety, dwell much longer in the blood; and because of this they form the majority of the circulating IgA. Blood concentration of IgA is high in man, a species whose blood seems to receive mostly monomeric IgA. It is much lower in the rat, mouse and dog, and in these species most of IgA entering the blood is probably oligomeric.