FUNCTIONAL-ANALYSIS OF ALPHA-1-BETA-1 INTEGRIN IN HUMAN NATURAL-KILLER-CELLS

Upon activation with interleukin (IL)-2 human natural killer (NK) cell s acquire on their surface the alpha 1 beta 1 and alpha 2 beta 1 integ rins and down-regulate the expression of alpha 6 beta 1. By employing alpha 1 beta 1-specific monoclonal antibody (mAb) HP-2B6, characterize d in our laboratory, we examined the functional role of the alpha 1 be ta 1 integrin in NK cells. Treatment with HP-2B6 mAb partially interfe red with attachment of cultured NK cells to type I collagen, and combi ned with an anti-alpha 2 beta 1 (TEA 1/41) mAb, it completely abrogate d cell adhesion to this extracelular matrix protein. In contrast, NK c ell attachment to laminin was completely blocked by the anti-beta 1 LI A 1/2 mAb, but was unaffected by alpha 1 and alpha 2-specific mAb; as alpha 3 beta 1 and alpha 6 beta 1 were undetectable, the data indicate that the alpha 1 beta 1 integrin binding sites for type I collagen an d laminin are different. Incubation with anti-alpha 1 HP-2B6 or its F( ab')(2) fragments specifically induced a rapid homotypic aggregation o f NK cells that was dependent on active metabolism, an intact cytoskel eton and the presence of divalent cations (Ca2+ and Mg2+); homotypic c ell adhesion was selectively blocked by anti-CD18, CD11a or CD54 mAb. In addition, stimulation of cultured NK cells with the anti-alpha 1 HP -2B6 enhanced TNF-alpha production and induced tyrosine phosphorylatio n of a 110-kDa protein. Pretreatment with specific inhibitors of prote in tyrosine kinase (PTK) activity (tyrphostin 25 and herbimycin A) com pletely abrogated the functional effects induced by the anti-alpha 1 H P-2B6 mAb. Our data show that ligation of the alpha 1 beta 1 integrin positively modulates IL-2-activated NK cell function via a PTK-depende nt pathway.