Pulmonary cell-mediated cytotoxicity in hamsters with parainfluenza virus type 3 pneumonia

A 51Cr-release cytotoxic assay in vitro was developed to permit definition of the role of local pulmonary cell-mediated immunity in the recovery phase of experimental parainfluenza virus type 3 pneumonia in the Syrian hamster. Cytotoxic effector cells were obtained by bronchalveolar lavage; virus-infected targets were syngeneic secondary hamster kidney cells. Maximal target-cell killing was mediated by lung lavage cells obtained one week after infection; the response waned rapidly thereafter. There was a close temporal correlation between the cytotoxic response and termination of virus replication in the lung. Cytotoxicity was virus specific and was restricted by a requirement for species identity between effector and target cells. Immune spleen cells mediated one-fourth the amount of 51Cr release effected by lung lavage cells, which suggests that cytotoxic effectors were concentrated in the lung. Although the identity of the cytotoxic effector cell was not established conclusively, the characteristics of the response suggested strongly that thymus-derived lymphocytes mediated lysis of target cells. Further work is required to determine the relative importance of this aspect of the host response during recovery from respiratory viral infection.