Antibody-Dependent Cellular Cytotoxicity (ADCC) Mediated by Human Killer Lymphocytes (K-Cells)

Abstract

During the past two decades a variety of in vitro procedures has been designed to elucidate the mechanisms of cellular immunity. The most thoroughly studied systems deal with the extracellular, nonphagocytic destruction of various types of “target” cells. Three major models of this cell-mediated cytotoxicity can be distinguished. (1) Certain cytolytic T lymphocytes (CTL) may destroy target cells after contact interaction mediated by lymphocyte receptors specific for surface antigens of the targets. These receptors are not conventional immunoglobulins and are synthesized by the cells that carry them. A further important feature of CTL-mediated cytotoxicity is its (major histocompatibility complex) MHC-restriction, i.e., CTL recognize foreign antigens only in association with “self”-MHC antigens [1]. (2) A variety of leukocytes, including polymorphs (PMN), mononuclear phagocytes, and certain lymphocytes may destroy target cells after similar cell-to-cell interactions but with humoral antibodies serving as the major target recognition factors (antibody-mediated cellular cytotoxicity, ADCC). Commonly, the effector cells exhibiting ADCC have surface receptors for the Fc-part of immunoglobulin (FcR), enabling them to interact with target cellbound antibody molecules. Since antibody-producing lymphocytes (B cells) are not active in ADCC, the effector cells are dependent on recognition factors (antibodies) produced by other cells.