The Effect of Virus-immune Serum on Anti-viral Cytotoxic T cells in vivo and in vitro

Abstract

Virus-immune sera applied to infected target cells inhibited Tc [cytototic thymus-derived] cell-mediated lysis in vitro. Blocking activity was clearly present in serum by 6 days after ectromelia virus infection. Activity was found in the Ig[immunoglobulin]G and IgM fractions of hyperimmune sera and was specific for the immunizing virus when ectromelia and influenza viruses were used, but did not distinguish between the serologically related poxviruses ectromelia, vaccinia and rabbitpox. There was no requirement for the donors of immune serum to be of the same mouse strain as the target cells, or the same species, since rabbit sera blocked similarly to mouse sera. Apparently virus-specified antigens recognized by B [bone marrow-derived] cells are physically close to, or identical to, the virus antigens involved in Tc cell-recognizable antigenic changes in infected cell surfaces. There was no evidence for modified H-2 molecules alone, or other proteins coded by derepressed host cell genes being recognized by virus-immune Tc cells. Significant inhibition of lysis by anti-viral antibody was only observed on fibroblast type target cells. Macrophage and P815 targets were refractory to blocking. These findings are discussed in practical terms and in relation to possible regulation of Tc cell responses in vivo by antiviral antibody.