Immunoglobulin A: site and sequence of expression in developing chicks.

Synthesis of immunoglobulins A, G, and M (IgA, IgG, and IgM) is prevented in chickens by embryonic treatment with heterologous antibodies to IgM when combined with bursectomy at hatching. Cells that produce IgA are seeded from the bursa of Fabricius later than cells capable of IgM and IgG synthesis; the latter do not convert to IgA synthesis outside of the bursa.