Turbidimetric microassay for macrophage-mediated antibody-dependent cellular cytotoxicity

An improved microassay for quantitation of murine macrophage-mediated antibody-dependent cellular cytotoxicity (ADCC) has been developed. The method is based on the turbidimetric measurement of sheep erythrocyte or nucleated (L1210) target cell suspensions at 630 nm with an automatic microtiter plate densitometer. The novel method was applied to demonstrate dose-related increases in murine macrophage mediated ADCC with varying antibody concentration, effector:target ratio, and incubation time. Advantages of the turbidimetric method were shown over the 51Cr-labeled target cell method by direct comparisons in that the new method was 2-4 times more sensitive and allowed repeated readings of the same plate after various incubation time intervals. The method provides further advantages of (1) elimination of the need for expensive and hazardous radioactive materials, (2) relative ease and rapidity in which experiments may be performed and quantitated, (3) sensitivity and reproducibility, and (4) versatility of the assay for measuring cytotoxicity of either erythrocyte or nucleated target cells.