Quantification and distribution of chicken immunoglobulins IgA, IgM and IgG in serum and secretions

IgA was found to be present in chicken serum in a concentration of 0.33 mg/ml, thus representing less than 4 per cent of total immunoglobulins. Of this amount, about 20 per cent appeared to be monomeric, most of the rest consisting of polymers greater than dimers. The average concentration of IgM in chicken serum was found to be 2.55 mg/ml. This comprised a small, hitherto undetected, monomeric fraction. IgA predominated in absolute amounts over other immunoglobulins in chicken bile and intestinal secretions, but not in saliva, tears and seminal plasma. In relative terms, however, every external secretion investigated was selectively enriched in IgA, as evidenced by a (IgA secretion)/(IgA serum):(IgG secretion)/(IgG serum) ratio greater than one