CHARACTERIZATION OF A NOVEL MONOCLONAL-ANTIBODY, EIV-E12, RAISED AGAINST ENRICHED SPLENIC ELLIPSOID-ASSOCIATED CELLS

A monoclonal antibody, EIV-E12, was produced against splenic ellipsoid -associated cells. In postnatal chicks, the antigen defined by EIV-E12 associated with about 90% of bursal cells and accumulated in B cell-r ich areas of lymphoid organs, The antigen was expressed by many spleni c cells on day 9 of embryogenesis and about 1 day later in the bursal anlage, where the cells positive for the antigen localized in close pr oximity to the plical epithelium. In the bursa, these early EIV-E12 ce lls appeared before Bu-1-positive cells and may represent a dendritic cell precursor. B cells within the developing bud acquired the EIV-E12 antigen, Immunoprecipitation studies revealed a molecular weight of 2 33 (nonreduced) and 205 (reduced) for the EIV-E12 antigen, These value s were markedly different from the molecular weight of the antigen ide ntified by Bu-l but similar to that of a CB10 antigen, The CB10 and EI V-E12 MAbs exhibited some differences in cellular staining, Taken toge ther these data suggest that EIV-E12 MAb recognizes a unique cellular population during embryogenesis.