Background: In the immune system, integrins have essential roles in leukocyte trafficking and function. These include immune cell attachment to endothelial and antigen-presenting cells, cytotoxicity, and extravasation into tissues (1). Integrin adhesion receptors transduce signals that control complex cell functions which require the regulation of gene expression, such as proliferation, differentiation and survival. Their intracellular domain has no catalytic function, indicating that interaction with other transducing molecules is crucial for integrin-mediated signaling. JAB1 (Jun activation domain-binding protein 1), a coactivator of the c-Jun transcription factor, has been identified as a protein that interacts with the cytoplasmic domain of the beta2 subunit of the alphaL/beta2 integrin LFA-1 (2). Patients with leukocyte adhesion molecule (CD11/CD18, beta 2 integrins) deficiency have structural defects in the common beta subunit (CD18), which prevent heterodimer formation and normal cell surface expression of these receptors, leading to life-threatening bacterial infections (3).