Influenza virus depresses the PFC response of mice by affecting T-cell function

Five influenza virus strains of type A and one strain of type B were used to elicit suppressive effect on the formation of antibody producing cells in response to sheep red blood cells (SRBC) both in vivo and in vitro. Not only live virus but also the formalin inactivated one exerted immunosuppression (IS). Although intranasal infection only could cause disease in mice, it exerted no IS which, in contrast, occurred after intraperitoneal or intravenous injection of the virus. In nude mice these effects were not seen, but they could be elicited when transferred with normal T cells. The antibody response to T cell independent antigen such as DNP was normal. Thus, it was proved that influenza virus induced T cell dependent immunodeficiency. However, T cell enriched population from infected mice when cultured with normal spleen cells could not suppress their PFC response in vitro. This suggested that suppressor T cells were not required for the immunodeficiency caused by influenza virus.