Chicken thymocyte antigen which participates in cell proliferations of thymocytes and tumour-derived lymphoid cell...

A novel antigen on chicken thymocytes was defined by CETHB1 and CETH46 monoclonal antibodies (mAbs) that were prepared against chick embryonic thymocytes. CETHB1 and CETH46 mAbs recognized different epitopes on the same membrane antigen (molecular weight: 76.2 kDa). These mAbs reacted with >80% of thymocytes of 14-day-old embryos to 8-week-old chickens. Almost all splenocytes, peripheral blood lymphocytes and bursa cells were negative, and only 7.7% of bone marrow cells were positive for both antibodies. In two-colour analysis with mAbs reacting to T cell markers (CD4 or CD8), most CETHB1 positive cells were CD4- CD8- or CD4+ CD8+. However, a proportion of CD4+ CD8- and CD4- CD8+ cells were negative for CETHB1 mAb. The proportion of thymocytes reacting with CETHB1 in chickens immunosuppressed by cyclophosphamide treatment increased gradually in parallel with the restoration of the thymus. An increase of CETHB1-positive cells was observed in thymocytes stimulated with Con A. Hence, it seems that the CETHB1 antigen expression on thymocytes is influenced by the thymic micro-environment and that the antigen may take part in thymic differentiation. Interestingly, CETHB1 antigen was expressed not only on T cell tumour-derived lymphoid cell lines, but also B-lymphoma-derived cell lines. The antigen expressions on these cell lines were observed only in the proliferative phase of the cells. Hence, the molecule which reacted with CETHB1 may be an antigen commonly expressed on lymphoma cells and may be involved in cell proliferation.