The Use Of Envelope Specific Monoclonal Antibodies To Search For Differentiation Antigens Encoded By Endogenous Retroviral Sequences In Murine Hematopoietic Cells
Hematopoietic cells in the mouse were examined to detect retrovirus encoded differentiation antigens on their cell surfaces. Twenty-four established lymphoid, erythroid, and myeloid cell lines were studied. A panel of well defined envelope specific monoclonal antibodies were tested against 125 each cell line in a I-protein A cell binding radioimmunoassay to detect retroviral envelope antigens on the cell's plasma membrane. Results were analyzed to discern cell line specific expression of antigens as a basis for the search for differentiation antigens. A few cell lines were selected for further study. Two erythroid cell lines, 7727 and 7883, for example, were studied because of their singular reactivity with the broadly reactive 18-1 antibody. The bulk of this study attempted to determine if the gp70 reacting with the antibody 18-1 was encoded by the Moloney/SFFV pseudotype virus used to induce the cell lines or originated from an endogenous retrovirus. If the envelope antigens were encoded by endogenous retrovirus they would be good candidates for differentiation antigens. Membrane immunofluorescence, cytoplasmic fluorescence, and immunoprecipitation and PAGE analysis were used to determine that the gp70 did, in fact, originate from the inducing Moloney/SFFV pseudotype virus. The expression of this Moloney antigen was determined to be defective. In addition, several myeloid cell lines proved to be noteworthy. They expressed antigens encoded by xenotropic endogenous virus in an unprece dented manner. These cell lines warrant further study since these antigens may be differentiation antigens. Continued use of the monoclonal antibody panel and the other cell lines utilized may also facilitate the search for these antigens in future research.