beta2 Integrins (CD18) are required for leukocyte migration. In fact, the absence of CD18 results in type-1 leukocyte adhesion deficiency (LAD-1). We analyzed the distribution phenotype and function of dendritic cells (DCs) in three LAD-1 patients with homozygous mutations of CD18. Two of them did not express CD18 (Patients A and C), and the other subject (Patient B) displayed reduced expression of beta2 integrins because of a missense mutation. Analysis of DCs derived from Patients A and B showed an abnormal morphology and a severe impairment in transendothelial migration and chemotactic response to CCL19/macrophage inflammatory protein-3beta, suggesting that CD18 is required for migration of monocyte-derived DCs. Nevertheless, DCs displayed normal macropinocytosis and underwent normal maturation after addition of tumor necrosis factor alpha. Finally, immunohistochemical analysis of lymph nodes from subjects B and C revealed a significant reduction in the number of factor-XIIIa(+) interstitial DCs in the interfollicular area in both patients, suggesting that CD18 plays a role in the migration of these cells in vivo.