Suppression of tuberculin hypersensitivity during influenza infection in mice

Tuberculin hypersensitivity was examined during acute influenza infection in mice. Employing the footpad test as a measure of delayed-type hypersensitivity, it was noted that tuberculin hypersensitivity was suppressed temporarily beginning on day 3 and continuing through days 10 to 16 following intranasal infection with influenza A/PR8. These changes occurred at a time when influenza virus was replicating in lung tissue. Suppression of footpad swelling was not detected when mice were administered live virus intravenously, were given Formalin-inactivated virus intranasally, or were immunized against influenza before intranasal infection. Transient reduction of total circulating lymphocytes also occurred during influenza infection but did not correlate with the duration of footpad suppression. Because this model system reproduces many of the alterations in immunological function reported to occur during influenza infection in humans, it should provide a useful tool for investigating mechanisms of influenza-induced immunosuppression.