Identification of chicken Bu-1 alloantigens using the monoclonal antibody AV20

The genetically polymorphic chicken antigen Bu-1 (chB6) has been identified by alloantisera raised against RPL line 6(3) (Bu-1a) and line 7(2) (Bu-1b) birds and subsequently by monoclonal antibodies (mAbs) which identify individual alloantigens. We have produced a monoclonal antibody, AV20, which recognises a monomorphic determinant on the antigen Bu-1. AV20 identifies a marker on both bursal and peripheral B cells. Staining characteristics on bursa, spleen, thymus and peripheral blood lymphocytes are similar to those of the allotypic antibodies which identify Bu-1a and Bu-1b. However, AV20 identified B cells in partially inbred birds as well as inbred lines including line 6(1) and line 7(2), indicating that it recognises a monomorphic determinant, AV20 immunoprecipitated an antigen with a Mwr of 150 kDa under non-reducing conditions and 70-75 kDa under reducing conditions indicating it is a homodimer. Serial immunoprecipitations or bursal-cell lysates from line 6(1) or line 7(2) confirmed that AV20 recognised the same antigen as mAbs against Bu-1a and Bu-1b in the respective lines.