P017 - CD47 REGULATES CD11B-DEPENDENT NEUTROPHIL TRANSEPITHELIAL MIGRATION DURING INTESTINAL INFLAMMATION
(Room Poster Hall)
19 Jan 18
5:30 PM
-
7:00 PM
Tracks:
Clinical and Research Challenges
Neutrophil (PMN) migration across the intestinal mucosa correlates with disease flares in individuals with IBD. Despite this correlation, molecular events regulating PMN transepithelial migration (TEpM) are still elusive. However, it is clear that the leukocyte integrin CD11b/CD18 and the ubiquitously expressed membrane glycoprotein CD47 play crucial roles in this process. We hypothesized that CD47 interacts with CD11b/CD18 to regulate PMN trafficking in the gut. In vivo ileal loop assays showed reduced PMN migration into the lumen of CD47-/- mice in response to LTB4 (>60% reduction vs WT; p<0.05). This reduction is not due to the loss of CD47 on intestinal epithelial cells, as there were no differences in PMN migration between VillinCreCD47fl/fl mice and control CD47fl/fl mice. In vitro assays demonstrated a 25% reduction in LTB4 driven TEpM with CD47-/- PMN. In addition, blocking CD11b/CD18 antibody (mAb) reduced WT PMN migration to levels similar to those observed with CD47-/- PMN. However, CD11b/CD18 mAb did not reduce migration of CD47-/- PMN further, suggesting that CD47 plays a role in regulating integrin-dependent chemotaxis. In co-immunoprecipitation assays, CD47 was observed to associate with CD11b in PMN. Furthermore, we observed that upregulation of CD11b upon stimulation was reduced in CD47-/- PMN compared to WT, despite expression of similar levels at baseline. Consistent with these results, we observed reduced upregulation of CD11b upon chemoattractant stimulation in CD47 deficient human neutrophil like HL60 cells. Lastly, using antibodies specific for high affinity conformation of CD11b/CD18, we observed reduced CD11b/CD18 activation in CD47 deficient HL60 cells. These data support a role for CD47 in regulating PMN TEpM through effects on CD11b/CD18 functions. Targeting CD47 may provide a new therapeutic approach aimed at reducing pathologic intestinal inflammation in IBD.