Role of bursin in the development of B lymphocytes in chicken embryonic Bursa of Fabricius

Localization and role of bursin during Bursa of Fabricius (BF) ontogeny wer e examined by immunohistochemical staining and by in ovo injection with ant i-bursin antibody. Mouse monoclonal anti-bursin antibody HU2 was generated by immunization with synthetic bursin. It recognized reticular cells (REC), follicular associated epithelium (FAE), FAE-supporting cells, and the basa l layer of interfollicular epithelium (IFE) in the mature BF. Bu-1(+) cells were first detectable in the mesenchyme area at 13 days of embryogenesis ( E13) before bud formation, then lined up along the bud, and homed into the bud at around E15. IgM(+) cells were detected in the bud after E13. Bursin was first observed at the under edge of the bud. Injection of HU2 into embr yonal vein at E13 suppressed the appearance of IgM(+) cells in the Bursa at E17. These results indicate that bursin exists beneath the bud and may act on the appearance of IgM(+) cells during BF ontogeny. (C) 2001 Published b y Elsevier Science Ltd.