antibodies that inhibit the reaction between ANTIGEN and other antibodies or sensitized t-lymphocytes (e.g., antibodies of the immunoglobulin g class that compete with IGE antibodies for antigen, thereby blocking an allergic response). Blocking antibodies that bind tumors and prevent destruction of tumor cells by CYTOTOXIC t-lymphocytes have also been called enhancing antibodies. (Rosen et al., dictionary of Immunology, 1989)