A novel leukointegrin, αdβ2, binds preferentially to ICAM-3

Abstract The leukocyte-restricted β2 (CD18) integrins mediate cell adhesion in a variety of events essential for normal immune function. Despite extensive research in this field, only three members of this Integrin subfamily have been described: C011 a/CD18 (LFA-1), CD11 b/ CD18 (Mac-1), and CD11c/CD18 (p150,95). We have identified a cDNA encoding a fourth a chain, ad, that associates with C018. The ad subunit is more closely related to CD11b and CD11c than to CD11a. This integrin is expressed at moderate levels on myelomonocytic cell lines and subsets of peripheral blood leukocytes, and more strongly on tissue-compartmentalized cells such as foam cells, specialized macrophages found In aortic fatty streaks that may develop into atherosclerotic lesions. The ad/CD18 molecule exhibits preferential recognition of ICAM-3 over ICAM-1.