Markers of B lymphocyte differentiation in the chicken.

A study was made of the ontogeny and tissue distribution of seven antigen systems associated with B lymphocyte development. A panel of seven monoclonal antibodies (MAbs) directed against avian bursal and peripheral B lymphocytes was developed. The spectra of cellular reactivity and size of respective antigens indicate that these MAbs appear to react with determinants of chicken B lymphocytes that had not been previously described. Immunofluorescence analysis of cell surface antigens using this panel indicated that dynamic changes in antigen expression are associated with early ontogeny and maturation of the B cell lineage. The yolk sac contained subpopulations of hematopoietic cells reactive with three MAbs (CB10, CLA3 and Hy86b5) which possibly mark the pre-bursal stem cell population. At or near the time of surface IgM expression in the embryonic bursa, B cells expressed antigens detected by the CB7, CB8, CB9 and CB11. In the juvenile chicken, CB7 reacted with immature bursal lymphocytes, while CB8, CB9 and CB10 reacted with bursal lymphocytes and a subpopulation of peripheral B lymphocytes. The antigens defined by Hy86b5 and CB11 were expressed on mature B lymphocytes but on only a subpopulation of bursal lymphocytes. The MAb CLA3 detected an antigen expressed on all leukocytes but not erythroid cells. Expression of some of these antigens by cells of the myelomonocytic lineages suggests a possible functional or ontogenetic relationship between the B lymphocyte and myeloid lineages.