Cell cooperation in antibody responses to influenza virus. I. priming of helper t cells by internal components of virion.

T cells recognizing internal components of the influenza virion can cooperate with B cells recognizing hemagglutinin to enhance the hemagglutinin inhibition (HAI) antibody response. Cooperation occurs only when the internal proteins and hemagglutinin are subsequently presented in association. The effect enhances the production of both 2-mercaptoethanol-resistant and -sensitive antibodies. The cooperating cells express the Thy-1+, Ly-1+2- surface phenotype and thus are characteristic of helper T cells. Immunization of mice with the internal components of the virion increases survival after exposure to lethal influenza infection. Mice primed with purified matrix protein produce enhanced amounts of HAI antibody after infection with influenza. These results may help to explain reports on the effects of heterotypic infection on antibody production, and also heterotypic immunity.