Abstract
Summary: Erythrocytes can be fixed with sulfosalicylic acid. The human blood group substances that have been tested are not destroyed The fiexd. cells behave differently toward hemagglutinin from influenza viruses in contrast to native erythrocytes. The stabilized cells can be coated with RNP-antigen prepared from infected chorioallantoic membranes and used in a sensitive indirect hemagglutination test for the detection of antibodies. RNP-antigen inhibits the hemagglutination reaction specifically. Blocking tests can therefore be used to titrate antigen-containing material.