title: Ontogeny and tissue distribution of the chicken Bu-1a antigen.
abstract: By using a sensitive technique of immunofluorescence on polyethylene glycol-embedded tissue sections, we could better determine the distribution of L22+ cells in embryonic and adult chickens. L22 mAb was originally described as reacting with bursa and bursa-derived lymphocytes. We now present evidence to suggest that this mAb also reacts with a subset of macrophages found in bursa, thymus, spleen, liver, intestine and peritoneum. The L22+ cells appear early during embryonic life, simultaneously in yolk sac, bursa, thymus, spleen and bone marrow. At all steps of their ontogeny, thymocytes were L22-, while most, if not all, bursal lymphoid cells were L22+. Moreover, L22 antigen can be detected on haemopoietic cells probably precursors, before and during their entry into the bursal rudiment on Day 9 or 10 of embryonic life. We conclude from these data that L22 is not restricted to the B-cell lineage as it is shared with a subset of macrophages. Furthermore, our observations of L22+ cells during embryonic life favour the hypothesis of separate lineages for B-cell and T-cell precursors in chick embryo, which was previously put forward on the basis of different sets of experiments.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000941:Antigens / Q000032:analysis*; D001402:B-Lymphocytes / Q000032:analysis*; D001853:Bone Marrow / Q000196:embryology / Q000276:immunology; D002060:Bursa of Fabricius / Q000196:embryology / Q000276:immunology*; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D008099:Liver / Q000276:immunology; D008264:Macrophages / Q000032:analysis*; D013154:Spleen / Q000196:embryology / Q000276:immunology; D013950:Thymus Gland / Q000196:embryology / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000941:Antigens