Characterization of duck leucocytes by monoclonal antibodies

cDNAs encoding CD3ε, CD4 and the α-chain of CD8 of ducks were cloned. Monoclonal antibodies against Pekin duck CD4 and CD8α revealed that the antigens were expressed by the majority of thymocytes and by subpopulations of CD3+ cells in peripheral tissues. CD8α cell surface expression was also found on 90% of bursal cells. The B cell specificity of a newly developed mab to the immunoglobulin light-chain (L-chain) was confirmed by double labelling studies with the chicken B-cell cytokine BAFF. Using these tools and a mab reacting with the cytoplasmic domain of CD3ε, we demonstrated that the CD8α molecule is expressed to high levels in CD3-positive T cells and at lower levels in CD3-negative bursal and peripheral B cells. Mab 2-4, which recognizes the chicken CD28 molecule, was found to react with CD4-positive duck lymphocytes and with CD8-positive duck T cells but not with CD8-positive B cells. Mab K1, which recognizes a common antigen on chicken thrombocytes and monocytes/macrophages, was found to react with duck thrombocytes and macrophages. Thus, a range of mabs is now available which will allow to phenotype the major leucocyte populations in ducks, a surrogate infection model for hepatitis B virus.