Expression of major histocompatibility complex antigens (H-B) on haemopoietic cells, lymphoid cells, and chick embryo fibroblasts from congenic lines of chickens.

The expression and distribution of chicken major histocompatibility antigens (H-B) was examined by electron microscopy. Using an indirect method of ferritin and peroxidase labelling with monospecific heteroantisera and with monoclonal antibodies, the H-B alloantigens could be localized at the plasma membrane of various cell types. The antigenic binding sites were quantified on mature erythrocytes, erythropoietic cells, heterophils, lymphoid cells of both thymus and bursa origin, and on cultured normal and Rous sarcoma virus-transformed chick embryo fibroblasts. The degree of labelling was higher in mature normoblastic erythrocytes and lymphoid cells than in other haemopoietic cells and fibroblasts when the heterospecific antisera were used. A larger number of antigenic binding sites was labelled by the monomeric monoclonal antibodies than by the polyclonal antisera. The distribution and aggregation of the specific label on the plasma membrane of cells other than erythrocytes, however, differed in the fixed and unfixed cells.