A study of the reaction between influenza virus and the cells of the excised and perfused ferret lung has yielded the following results: (1) The cells of the lung rapidly adsorbed large amounts of intratracheally inoculated virus. (2) After a short interval the pulmonary cells began spontaneously to release the adsorbed virus, and in the case of influenza B the release was 75 per cent complete after 5 hours. (3) The Lee strain was more completely released from pulmonary cells after 5 hours than was the PR8 strain. (4) After the cells released the adsorbed virus they appeared incapable of adsorbing virus as before. (5) When the mouse-infecting capacity of the virus had been done away with by heat or formalin, the virus was adsorbed by the pulmonary cells but was not released.
In all except the last of the characteristics listed the interaction between influenza virus and the pulmonary cells closely resembles that between influenza virus and avian red blood cells.
In the living ferret inhaled influenza virus was also rapidly adsorbed by the lung, but in a very short time the adsorbed virus which at first could be readily eluted (after perfusion and excision of the lung) became so much more firmly fixed as not to be released by this method. Free virus could not be demonstrated in the living ferret until 24 hours after the animal had been exposed to the inoculum.
On the basis of these and previous experiments it is postulated that the destruction of a specific receptor substance,—which may involve an enzymatic reaction,—may be a necessary preliminary event in the parasitism of susceptible cells by influenza virus.