The effect of various anti-immunoglobulin G (IgG) antibodies on the complement-mediated lysis of herpes simplex virus-infected human fibroblasts was determined. IgM rheumatoid factor, a naturally occurring anti-human Fc, inhibited lysis, whereas rabbit anti-human IgG serum potentiated immune cytolysis. We attempted to explain this disparity by determining the effect various classess of anti-IgG's with differing specificities had on complement-mediated lysis. Inhibition of cytolysis occurred with IgM anti-Fc and all of the IgG antiglobulins (anti-IgG, Fab, and Fc). In contrast, IgM anti-Fab enhanced lysis. IgM anti-IgG suppressed immune cytolysis when high concentrations of antiviral serum were incubated with the virus-infected cell, but augmented lysis when low concentrations of anti-herpes simplex virus antibody were exposed to the fibroblasts. The experiments indicated that whether a particular antiglobulin potentiates or inhibits lysis depends on the concentration of antibody bound to the target cells as well as the class and specificity of the antiglobulin exposed to the antibody-coated cell.
The ability of IgG anti-Fc and anti-Fab to neutralize infectious herpes simplex virus-IgG (HSV-IgG) complexes was determined. When limiting amounts of antiglobulin were used, antibody directed against the Fab portion of human IgG was significantly more effective than anti-Fc antibodies in neutralizing the HSV-IgG complexes. The detection of viral bound antibody was enhanced by the incorporation of heterologous antiglobulin or complement in the antiglobulin neutralization test. Specifically, HSV-IgG which had been incubated with rabbit antihuman globulin was further neutralized by goat antirabbit IgG or guinea pig serum complement. This augmented neutralization test could prove useful in detecting small amounts of antibody bound to virus in infectious isolates from patients or experimental animals with viral diseases.
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