Inhibition by rheumatoid factor, anti-FC, and staphylococcal protein A of antibody-dependent cell-mediated cytolysis against Herpes simplex virus-infected cells.

Incubation of herpes simplex virus-infected human fibroblasts with the serum from a patient with herpes labialis rendered the cells susceptible to immune lysis by human mononuclear leukocytes (MNL) as well as complement. If, before the addition of MNL, the antibody-treated, infected monolayers were incubated with either IgM rheumatoid factor (RF), staphylococcal protein A (SPA), or anti-Fc gamma serum, antibody-dependent cell-mediated cytolysis (ADCC) was markedly depressed. SPA and anti-Fc caused maximal inhibition (greater than 90%), whereas RF resulted in a 72% depression. The inhibition of ADCC was dependent on both the concentration of the Fc-reacting materials incubated with the antibody-coated target cells and the concentration of antiviral antibody incubated with the virus-infected fibroblasts. Experiments indicated that the Fc-reacting materials depressed ADCC at the target cell level by covering or altering Fc sites on cell-bound antiviral antibody.