Analysis of the Adhesion Step in the Herpes Simplex Virus Antibody-Dependent Cellular Cytotoxicity System

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Abstract
The lysis of herpes simplex virus-infected tissue culture cells by antibody[Ab]-dependent cellular cytotoxicity (ADCC) requires a preliminary step in which effector cells adhere to the immunoglobulin G Ab-coated targets. Some of the mononuclear cells in human blood form rosettes with Ab-coated target cells. Most ADCC effector cells can be removed by allowing mononuclear cells to adhere to monolayers of Ab-sensitized tissue culture cells. The effect of various experimental conditions on the adhesion step was assessed in ADCC cultures at 1 g and after centrifugation. At 1 g, rosette formation and monolayer adhesion were partially reduced at 4.degree. C as compared to 37.degree. C. Both were partially inhibited in glucose-free medium containing sodium azide and 2-deoxyglucose but were unaffected in glucose-free medium containing only 1 of these energy inhibitors. After centrifugation neither reaction was inhibited at 4.degree. C or in glucose-free medium with sodium azide and 2-deoxyglucose. Cytochalasin B but not colchicine suppressed both reactions. Inhibition by cytochalasin B could not be reversed by centrifugation. Both reactions were independent of extracellular Ca2+ and Mg2+ and were unaffected by rendering mononuclear cells cytotoxically inactive by brief heat shock. The adhesion step in ADCC directed against virus-infected or uninfected tissue culture cells may be only modestly dependent on effector cell energy generation. Centrifugation may greatly reduce this dependence. Microfilaments but not microtubules may be necessary. The modest ambient temperature and energy requirements, independence of extracellular divalent cations, lack of sensitivity to colchicine and relative resistance to supraphysiological temperature serve to distinguish the adhesion step from the lytic step in ADCC.