Flow cytometry evaluation of cytotoxicity exerted by effector immune cells against tumor cells

Adoptive cell therapies based on immune effector cells - Natural Killer (NK) cells, Cytotoxic T Lymphocytes (CTL) - represent a promising approach for the treatment of resistant tumors, especially for the management of hematological malignancies. The rapid growth of this field emphasises the need for reliable in vitro methods to evaluate the cytotoxic potential of the cell products developed against the desired target cells, many of which are cells in suspension and consequently pose additional technical challenges. Here, we present a flow-cytometry-based protocol for the quantification of tumor cell death after co-culture with immune effector cells. Compared to earlier techniques, this approach allows for the identification of target cells and quantification of both their basal and effector cell-induced apoptotic death. The protocol described is highly adaptable, making it suitable for the study of fragile or limited patient samples, the evaluation of combination therapies with drugs or antibodies, and for the analysis of additional cellular markers or cell death mechanisms. Altogether, the protocol provides an assay setup and gating strategy that generate precise and reproducible data, essential for adoptive cell therapy optimization.