97th DOG Annual Meeting 1999



M. D. Becker, S. R. Planck, W. S. Blackman, J. T. Rosenbaum

To determine the role of the murine interleukin-8 receptor homolog (mIL-8Rh, neutrophil chemokine CXC receptor 2) in leukocyte migration using intravital microscopy in a standardized model of eye inflammation, endotoxin-induced uveitis (EIU).

Methods: 250 ng E. coli endotoxin was injected into the vitreous of knockout mIL-8Rh-/- (n=5) mice or heterozygous littermate mIL-8Rh+/- controls (n=5) (Science 1994, 265:682). Intravital microscopic examination of rhodamine-stained leukocytes in the iris microvasculature was performed at baseline, 6 hours and 24 hours after endotoxin injection. The numbers of rolling (cells/mm2 endothelial surface/min), sticking (cells/mm2 endothelial surface) and infiltrating cells (cells/mm2 iris tissue) were evaluated by digital off-line quantification.

Results: At 6 h, mIL-8Rh-/- mice had significantly fewer infiltrating cells than the heterozygous controls. The median (25, 75 percentile) values were 2 (0, 6) cells/mm2 for the knockouts and 67 (42, 168) cells/mm2 for the controls, p = 0.016 by Mann-Whitney Rank Sum test. At 24 h, the mIL-8Rh-/- animals tended to have fewer infiltrating cells, 0 (0, 23) cells/mm2 vs. 71 (13, 201) cells/mm2, but the values were not statistically different, p = 0.095. In contrast to tissue infiltration, the absence of the IL-8 receptor homolog did not reduce rolling or sticking.

Conclusion: Iris rhodamine angiography allows precise quantification of leukocyte-endothelial dynamics in the absence of surgical trauma. IL-8 and its homologs are known to be potent signals for leukocyte migration. IL-8 has also been localized to the endothelium and implicated in adhesion. We found the absence of the mIL-8Rh had relatively little effect on rolling or arrest but did decrease cell migration.

Casey Eye Institute, Oregon Health Sciences University, Portland, Oregon, 97201, USA