Monocytic cells synthesize, adhere to, and migrate on laminin-8 (alpha(4)beta(1)gamma(1))

Laminins, a growing family of large heterotrimeric proteins with cell adhes ive and signaling properties, are major components of vascular and other ba sement membranes. Expression, recognition, and use of laminin isoforms by l eukocytes are poorly understood. Tn monoblastic THP-1 cells, transcripts fo r laminin gamma (1)-, beta (1)-, and alpha (4)-chains were detected by RT-P CR. Following immunoaffinity purification on a laminin beta (1) Ab-Sepharos e column, laminin beta (1)- (220 kDa), gamma (1)- (200 kDa), and alpha (4)- (180/200 kDa) chains were detected by Western blotting in THP-1 cells and in two other monoblastic cell lines, U-937 and Mono Mac 6. After cell perme abilization, a mAb to laminin gamma (1)-chain reacted with practically all blood monocytes by immunofluorescence flow cytometry, and laminin-8 (alpha (4)beta (1)gamma (1)) could be isolated also from these cells. Monoblastic JOSK-I cells adhered constitutively to immobilized recombinant laminin-8, l ess than to laminin-10/11 (alpha (5)beta (1)gamma (1)/alpha (5)beta (2)gamm a (1)) but to a higher level than to laminin-1 (alpha (1)beta (1)gamma (1)) . Compared with the other laminin isoforms, adhesion to laminin-8 was prefe rentially mediated by alpha (6)beta (1) and beta (2) integrins. Laminin-8 a nd, to a lower extent, laminin-1 promoted spontaneous and chemokine-induced migration of blood monocytes, whereas laminin-10/11 was inhibitory. Altoge ther, the results indicate that leukocytes, as other cell types, are able t o synthesize complete laminin molecules. Expression, recognition, and use o f laminin-8 by leukocytes suggest a major role of this laminin isoform in l eukocyte physiology.