The use of indium-111 for studies of cytotoxicity mediated by lymphocytes or by antibodies and complement.

Mouse P815 mastocytoma cells, Meth A sarcoma cells and human MRC5 fibroblasts and peripheral blood mononuclear cells were labelled with 111In, 51Cr or 125IUdR and their release from the cells measured. Spontaneous release of 111In from the cells in cultures was less than half that of 51Cr and was comparable to the release of 125I. When 111In-labelled P815 cells were lysed with antibodies and complement or with sensitized lymphocytes the label was released rapidly. 111In is a convenient label in short- as well as in long-term in vitro cytotoxicity studies because of its high labelling and detecting efficiency and its stable cell association.