Identification of the avian B-cell-specific Bu-1 alloantigen by a novel monoclonal antibody.

A panel of monoclonal antibodies was generated against the guinea fowl's bursal cells. One of the antibodies, designated BoA1, recognized both cortical and medullary B cells of bursal follicles and B cell dependent regions of peripheral lymphoid organs, like germinal centers and splenic periellipsoidal regions. The staining pattern of this monoclonal antibody is similar to other antibodies (L22, 11G2, AV20), which also identify the Bu-1 antigens. Under reducing conditions, the molecular weight of the BoA1 antigen is 70 to 73 kDa, and after immunoprecipitation it proved to be identical with the antigen recognized by the AV20 antibody. It is unique for this novel monoclonal antibody that it shows wide range cross-reactivity with different avian species, like chicken, quail, guinea fowl, and turkey. Therefore, this Bu-1-specific monoclonal antibody could be a versatile tool for studying the B cell development in different domesticated birds.