A quantitative study of the membrane antigens on leukaemic and normal T cells in the PVG rat

Membrane antigens on PVG leukaemic cells have been compared with those on normal PVG peripheral T cells by studying the capacity of the cells to bind antibodies against these cell types. The antibody bound has been quantitated by secondary binding of a radiolabelled anti-immunoglobulin. It was shown that the leukaemic cell lacks the peripheral thymus-derived lymphocyte antigens which the normal PVG peripheral T lymphocyte carries. In this respect, in its reduced distribution of the W3/13 antigen compared with T cells, as revealed by binding of the hybridoma monoclonal antibody W3/13, and in its abundance of Thy 1.1 antigen, the leukaemic cell resembles the immature thymocyte, rather than the mature T lymphocyte. This antigenic profile represents an illustration of de-differentiation of tumour cells at the molecular level. Two antigens shared by PVG leukaemic cells, normal PVG peripheral T cells and thymocytes were indicated by absorption studies with antisera against the leukaemic cell. In an immunotherapy model, treatment with AUG cells sensitized against the PVG leukaemia cell resulted in elimination of leukaemic cells from PVG rats. The peripheral T cell antigens clearly cannot be antigen(s) recognized by the AUG rat on the leukaemic cell, since the present studies indicate the absence of peripheral T cell antigens on this cell.