Integrin ITGAL/ITGB2 is a receptor for ICAM1, ICAM2, ICAM3 and ICAM4 (PubMed:2051027). Integrin ITGAL/ITGB2 is a receptor for F11R (By similarity). Integrin ITGAL/ITGB2 is a receptor for the secreted form of ubiquitin-like protein ISG15; the interaction is mediated by ITGAL (PubMed:29100055). Involved in a variety of immune phenomena including leukocyte-endothelial cell interaction, cytotoxic T-cell mediated killing, and antibody dependent killing by granulocytes and monocytes. Contributes to natural killer cell cytotoxicity. Involved in leukocyte adhesion and transmigration of leukocytes including T-cells and neutrophils (PubMed:16234355, PubMed:24158516). Required for generation of common lymphoid progenitor cells in bone marrow, indicating the role in lymphopoiesis (PubMed:25108025). Integrin ITGAL/ITGB2 in association with ICAM3, contributes to apoptotic neutrophil phagocytosis by macrophages. Heterodimer of an alpha and a beta subunit. The ITGAL alpha subunit associates with the ITGB2 beta subunit. Interacts with THBD. Leukocytes. The integrin I-domain (insert) is a VWFA domain. Integrins with I-domains do not undergo protease cleavage. The I-domain is necessary and sufficient for interaction with ICAM1 and F11R. In resting T-cells, up to 40% of surface ITGAL is constitutively phosphorylated. Phosphorylation causes conformational changes needed for ligand binding and is necessary for the activation by some physiological agents. Mice show decreased cellularity in thymus but not spleen, and impaired early T cell development (PubMed:25108025). Obese mutant mice show decreased total number of T-cells, lower levels of neutrophil elastase and reduced cytotoxic T-cell proliferation in adipose tissue, as well as improved glucose tolerance and insulin resistance in comparison to obese wild type mice (PubMed:24158516). Splenocytes from mutant mice do not respond to extracellular Isg15 as demonstrated by lack of Ifng secretion in contrast to wild-type cells which secrete Ifng in response to treatment with Isg15 (PubMed:29100055). Belongs to the integrin alpha chain family.