Used in research to quantify Fas ligand (FasL) levels in biological samples such as serum, plasma, and cell culture supernatants. Enables investigation of apoptosis-related processes in immune regulation, cancer development, and autoimmune diseases. Commonly applied in studies involving T-cell activation, immune evasion by tumors, and cytotoxicity mechanisms. Supports biomarker discovery and evaluation of therapeutic interventions targeting the Fas/FasL pathway.