Specific identification of lysed target cells in a heterogeneous population by a double-fluorescent label technique

A double-fluorescent label method for the specific identification of target cells during cytotoxicity testing of a mixed cell population is described. When used for the detection of pancreatic islet cell surface antibodies, damaged cells are identified by the uptake of ethidium bromide (see as cells with orange nuclei when examined under rhodamine filters) and the various islet cell types are simultaneously identified by indirect immunofluorescent staining with the appropriate islet hormone antiserum and FITC-conjugated second antibody (seen as cells with green cytoplasma when examined under fluorescein filters). In this way, we have shown the insulin-containing beta cell to be the target of islet cell surface antibodies. This technique may be particularly useful in the study of autoimmune endocrine diseases where in vitro cytotoxicity testing would involve target cells intermixed with other cell types (e.g., adrenal gland, pituitary of gonadal tissue).