LAT (linker for activation of T-cells) is a 36 kD phospho-tyrosine adaptor protein containing SH2 domains and a CVRC motif. Two LAT isoforms have been reported with approximate molecular weights of 36 kD and 38 kD. LAT is localized to lipid rafts, and is also a potential type III transmembrane protein, thought to be expressed in the juxtanuclear intracellular compartment. LAT links TCR engagement to Ras-MAPK activation, Ca2+ flux, IL-2 expression and is required for T-cell development. LAT is phosphorylated when activated by TCR cross-linking, where it recruits signaling molecules. LAT activation can be prevented by polyunsaturated fatty acids. LAT is modified by ZAP-70 and Syk phosphorylation and can also be palmitoylated. LAT has been reported to be associated with Grb2, Gads, Grap, PLC-gamma1, p85 subunit PI3K, ZAP-70, Syk, Itk, Vav, SLP-76, and cbl. The LAT1111 monoclonal antibody recognizes the cytoplasmic domain of human LAT and has been shown to be useful for Western blotting and immunoprecipitation. The LAT1111 antibody does not cross-react with mouse LAT.