Neutrophil differentiated HL-60 cells model Mac-1 (CD11b/CD18)-independent neutrophil transepithelial migration

During active intestinal inflammation granulocytes accumulate in the lumen of the gut where they damage the epithelium through the release of various products such as reactive oxygen species and proteolytic enzymes. Previously, using function blocking monoclonal antibodies, we showed that neutrophil migration across intestinal epithelial monolayers in response to various chemoattractants was partially beta(2) integrin Mac-1 (CD11b/CD18)-independent. Here, we show that treating neutrophils with intact monoclonal antibody (mAb) to CD18 activates the cells to express more CD11b. Thus our goal now was to determine whether neutrophil Mac-1-independent transepithelial migration proceeds independently of prior cell activation through Mac-1. We took two approaches, one using blocking Fab' fragments of mAb to CD18 and the second was to develop a neutrophil differentiated HL-60 cell line which is Mac-1 deficient to further study neutrophil/epithelial cell interaction. Anti-CD18 Fab' minimally activated neutrophils but inhibited approximately 75% of transepithelial migration to fMLP while having a minimal effect (