Inhibition of Cytotoxicity of Nonimmune Human Lymphocytes for Sensitized Chicken Erythrocytes by Aggregated Human IgG

Human IgG is shown to inhibit the cytotoxic activity in vitro of human lymphocytes for chicken erythrocytes sensitized with rabbit antibodies. The inhibitory activity depends on the degree of aggregation of IgG, small complexes of 9 to 10 S being more inhibitory than monomeric molecules or heavy‐weight aggregates. For the immunoglobulin to be inhibitory, an intact Fc fragment is required. It is suggested that the inhibition is due to the binding of aggregated human IgG to lymphocytes needed in the cytotoxic reaction