Secretory Piece Determinants

The secretory IgA molecules characteristic of the body secretions such as saliva, tears, and milk contain a fourth polypeptide component termed secretory piece. In contradistinction to the situation with J chain, secretory component has prominent antigenic determinants which are displayed in the intact secretory IgA molecule. In fact, the presence of these determinants was very important in elucidating the unique char- 

As indicated in Table IV, allotype-specific antigenic determinants on rabbit secretory piece have been described by Knight et al. (1974). These markers have been shown to be unlinked to those associated with the other polypeptide chains found in rabbit immunoglobulins that were discussed previously. 

Dubiski, S., 1969, Protides Biol. Fluids Proc. Colloq. 17 117. 

Dubiski, S., Rapacz, J., and Dubiska, A., 1962, Acta Genet. Stat. Med. 12 136. 

and Laurell, A. B., 1956, Acta Pathol. Microbiol. Scand. 39 390. 

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We have discussed evidence for the presence of an IgA-like molecule in chickens. In brief, the chicken protein has antigenic determinants not shared by IgG or IgM, is found in relatively high concentration in secretory fiuids, and is selectively synthesized by plasma cells in the lamina propria of the gut. In addition, this protein, alone among chicken immunoglobulins, is capable of binding human secretory piece (97). 

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