AITRL, a member of the TNF superfamily, is expressed in endothelial cells, and signals through the AITR receptor. AITRL regulates T cell proliferation and survival, and effectuates the interaction between T lymphocytes and endothelial cells. The AITRL gene codes for a type II transmembrane protein comprised of 177 amino acids, including a 28 amino acid cytoplasmic region, a 21 amino acid transmembrane domain and a 128 amino acid extracellular domain. Recombinant Human soluble AITRL is a 14.4 kDa protein, containing 127 amino acid residues corresponding to the extracellular domain of AITRL.