A highly sensitive and reproducible microcytotoxicity assay for demonstrating cytotoxic antibodies to cell surface antigens.

An assay is described, in which target cells are suspended in diluted rabbit serum (as a source of complement) and pipetted into the wells of Falcon No. 3034 Microtest plates, to which diluted antiserum (or control serum) has been added. After 18--24 h of incubation, the plates are stained with crystal violet and counted using an electronic Quantimet image analyzer. This technique could reproducibly detect complement-dependent cytotoxic antibodies to target cell H-2 antigens and to MuLV gp70 on cell lines which expressed this antigen, at serum dilutions up to 1:160,000. The cytotoxic antibodies could be removed by absorption of sera with cells carrying the respective antigens.