Inhibition of Spontaneous and Antibody‐Dependent Cellular Cytotoxicity by Sera and Isolated Antiglobulin Preparations from Rheumatoid Arthritis Patients

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Abstract
Using sera from patients with rheumatoid arthritis and antiglobulin preparations obtained from such sera, inhibition of human lymphocyte cytotoxicity in antibody-dependent (ADCC) and spontaneous cell-mediated cytotoxicity (SCMC) reactions against an allogeneic melanoma cell line (IGR3) was demonstrated. Fractionation of effector cell preparations indicated that Fc-receptor-bearing lymphocytes were operative in both reactions. Removal of phagocytic and adherent cells from the effector cell population resulted in more pronounced inhibition of SCMC and ADCC reactions by rheumatoid sera. Antiglobulin preparations from human sera containing rheumatoid factor activity can apparently effectively block the cytotoxic activity of Fc-receptor-bearing effector lymphocytes (K cells) in vitro. On analogy with the inhibition of ADCC and SCMC reactions by immune complexes and aggregated Ig[immunoglobulin]G, antiglobulin complexes present in the antiglobulin preparations are responsible for this effect.