[Antigenic determinants of the hemagglutinins of influenza viruses of the "Spanish era"].

: Fractions of immunoglobulins G isolated from highly active hyperimmune rabbit sera and inhibitor-free antisera for influenza A viruses of the "Spanish" era different periods (1930-1978) were tested with a wide spectrum of human and animal viruses by the HI and CF tests. In hemagglutinins of Hswl, H0, and H1 viruses common antigens were found dissimilarly expressed in different variants as indicated by both various degrees of serological activity of the viruses and by great differences in the availability of cross-reactive antibody in various sera.