Phospho-LAT (Tyr191) antibody detects the activated form of the linker for activation of T cells (LAT), a transmembrane adaptor protein critical for T-cell receptor (TCR) signaling. LAT is tyrosine-phosphorylated upon TCR engagement, with Tyr191 being a key residue phosphorylated by ZAP-70/Syk kinases. This phosphorylation creates docking sites for SH2 domain-containing signaling molecules like PLCγ1. Grb2. and SLP-76. facilitating downstream pathways such as calcium flux, MAPK activation, and cytokine production. The antibody specifically recognizes LAT phosphorylated at Tyr191. serving as a marker for early TCR signaling events. It is widely used in immunology research to study T-cell activation, immune synapse formation, and dysregulated signaling in autoimmune diseases, immunodeficiencies, or cancers. Applications include Western blotting, immunofluorescence, and flow cytometry to assess LAT activation status in cell lines, primary lymphocytes, or tissue samples. Validation often involves stimulated versus unstimulated T-cells or LAT-deficient cells to confirm specificity. Its utility extends to preclinical models for evaluating therapeutic interventions targeting TCR signaling pathways.