Studies of the Determinant Antigens of Viable Cells

Abstract

Summary Human epidermoid carcinoma No. 2 (HEp-2) cells infected with herpes simplex virus and treated with rabbit anti-HEp-2 serum and fresh guinea pig complement failed to produce plaques when seeded on HEp-2 monolayer cultures. Antiserum alone or complement alone were ineffective. This observation is in accord with the concept that virus multiplication requires viable cells. This method for studying immune cytolysis was used to differentiate in a quantitative fashion between intact cells and cells injured by the combined action of antibody and complement. The test system was suitable for titration of complement and for evaluation of the relationship between the number of cells in the test system and the amount of antibody required to reduce the plaque count by 50%. The sole function of infected cells was to provide a measurement of the fraction of the test population that remained viable after exposure to antibody and complement. Infected and noninfected cells reacted equally well with antibody and complement. The differentiation of viable from nonviable cells was not affected by the type of monolayer cell culture used for enumeration of infective centers. Comparative studies were made of stock HEp-2 cells and progeny of survivors of cells grown in the presence of antibody and treated with antibody and complement. Lower complement titers were observed in tests employing the progeny of cells which survived exposure to antibody and complement. However, it is not known whether the altered reactivity of these cells is a manifestation of increased resistance to immune injury or altered antigenic structure.