The interactions of hemagglutinating viruses with membranes of erythrocytes and cultured cells will be analyzed by immune electron microscopy and correlated immunochemical methodology. The agents to be used include paramyxoviruses (types 1 and 2), pseudomyxoviruses (measles, respiratory syncytial virus, pneumonia virus of mice), adenoviruses and reoviruses. Erythrocytes and cultured cell membranes will be fractionated to obtain pure soluble glycoprotein receptor substances which will be analyzed by inhibition of viral hemagglutination, hemolysis and hemadsorption. Corresponding antisera will be used for immunochemical analysis of the cell fractions in relation to their overall role in membrane structure and function. The cold agglutinating cross-reactive IgM evoked in humans by infection with Mycoplasma pneumoniae and by immunization of rabbits will be analyzed with particular reference to blood group determinants contained in the purified receptor glycoprotein. Membrane changes accompanying the establishment of persistent infections (PVM, measles) will be analyzed by immune-electron microscopy with appropriate antisera to virus and normal cells. BIBLIOGRAPHIC REFERENCES: Bachi, T., Deas, J.E. and Howe, C. "Virus-Erythrocyte Membrane Interactions" in Virus Infection and the Cell Surface (G. Poste and G. Nicholson, Editors) North Holland-American Elsevier, 1976, press. Duffy, P.D. and Howe, C. Rhesus erythrocyte glycoprotein receptors for measles virus. Abstract (S167) Annual Meeting, American Society for Microbiology, Atlantic City, 1976.