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

Abstract

The occurrence of mRNAs encoding μ, υ and υ(ΔFc) immunoglobulin heavy chains and λ 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 μ 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 λ message paralleled that of μ. Messenger RNAs encoding one or both of the υ 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 υ(ΔFc) message was detected prior to the υ message and predominated during the experiment; Harderian gland expressed the υ(ΔFc) 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(ΔFc) are probably not simultaneous products of the same plasma cells.