Duck lymphoid organs: their contribution to the ontogeny of IgM and IgY

The occurrence of mRNAs encoding mu, nu and nu(delta Fc) immunoglobulin heavy chains and lambda light chains in organs of duck embryos from 16 days of incubation and ducklings up to 74 days of age was assessed by Northern hybridization. The mu message was first detected in bursa of Fabricius and spleen at 16 days of incubation and in cervical lymph nodes at 23 days of incubation, but in other organs (bone marrow, buffy coat, Harderian gland, liver) not until 7 17 days after hatching; in general, the appearance of the lambda message paralleled that of mu. Messenger RNAs encoding one or both of the nu isoforms were first detected in cervical lymph nodes at 25 days of incubation, in spleen and bursa in 1-day-old ducklings, in Harderian gland, bone marrow and liver from 10 to 17 days post-hatching and in buffy coat from 46 days. In most organs, the nu(delta Fc) message was detected prior to the nu message and predominated during the experiment; Harderian gland expressed the nu(delta Fc) message exclusively. These results indicate that bursa of Fabricius, spleen and cervical lymph nodes play early roles in the development of B cells and the ontogeny of duck immunoglobulins while other lymphoid organs support the later differentiation of plasma cells, and that IgY and IgY(delta Fc) are probably not simultaneous products of the same plasma cells.