CD11dCD18

CD11dCD18, also known as αDβ2 integrin, is a heterodimeric adhesion receptor formed by the CD11d (ITGAD) alpha chain and the CD18 (ITGB2) beta chain. It belongs to the β2 integrin family, which mediates leukocyte adhesion and trafficking. The αDβ2 integrin is expressed on subsets of leukocytes, including monocytes, macrophages, dendritic cells, natural killer cells, and some T lymphocytes; expression is typically upregulated on activation and in inflammatory conditions.

In physiological terms, CD11dCD18 mediates firm adhesion of leukocytes to the vascular endothelium and to extracellular matrix, facilitating leukocyte extravasation and migration into tissues. It participates in interactions with a range of ligands, including intercellular adhesion molecule family members such as ICAM-3, with broader ligand recognition that can depend on the cellular context and activation state. The integrin can signal bidirectionally: inside-out signaling increases its affinity and avidity, while outside-in signaling influences adhesion strength, cytoskeletal organization, and cellular responses such as migration and phagocytosis.

Clinical and research relevance is largely centered on its role in inflammatory responses. Experimental models suggest that blockade or genetic deficiency of CD11dCD18 can reduce monocyte and macrophage recruitment to inflamed tissues, highlighting its potential as a target in inflammatory diseases. Compared with other β2 integrins like LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18), αDβ2 has a distinct tissue distribution and ligand repertoire, contributing to complementary roles in leukocyte trafficking and immune surveillance.

See also ITGAD, ITGB2, integrins, leukocyte adhesion.