Intraocular leukocyte response after IL-23 intravitreal injection as measured by intravital microscopy

Abstract

Purpose: Uveitis is frequently associated with spondyloarthritis. Innate lymphoid cells that express the receptor for interleukin-23 (IL-23) have been recently implicated in the pathogenesis of ankylosing spondylitis (Sherlock et.al., Nature Medicine, 2012). However, it is unclear whether IL-23 plays a major role in the intraocular inflammation characteristic of spondyloarthropathies. We examined the leukocyte response within the eyes of mice after intravitreal injections of IL-23.

Methods: We injected IL-23 (100 ng/2 µl) into the vitreous of the right eye of BALB/c mice. Using intravital microscopy. we observed the leukocyte responses in the iris vessels at 6 hours (n=10) and at 24 hours (n=7) after IL-23 injection. We also injected different concentration of IL-23, 1 µg/2 µl (n=5) and monitored the same response at 3 hours and 6 hours after the injection

Results: Intravital microscopy revealed slow blood flow of iris vessels in 4 out of 10 mice at 6 hours and in 3 out of 7 mice at 24 hours in the IL-23 100 ng group. The average number of rolling leukocytes was 1803/min/mm² at 6 hours and 1600/min/mm² at 24 hours in the 100 ng group, compared with 1310/min/mm² at 6 hours and 750/min/mm² at 24 hours in the contralateral, saline-injected control eye. Leukocyte rolling was significantly increased at 24 hours after 100 ng of intravitreal IL-23 (p<0.05), but rolling was not significantly increased at other time points or after other concentrations of IL-23.The average number of sticking leukocytes was 91.7/mm² at 6 hours and 108/mm² at 24 hours in the 100 ng group, compared with 80.5/mm² at 6 hours and 75.2/mm² at 24 hours in the contralateral control eye. The average number of extravasated infiltrating leukocytes was 199/mm² at 6 hours and 133/mm² at 24 hours in the 100 ng group, compared with 141/mm² at 6 hours and 129/mm² at 24 hours in the contralateral control eye. Leukocyte sticking and infiltrating were not significantly increased at 6 hours and 24 hours after 100 ng of intravitreal IL-23 (p>0.05) and at other concentrations of IL-23.

Conclusions: Our data show blood flow changes and a transient increase in rolling leukocytes in iris vessels after IL-23 intravitreal injection. Further studies for the presence of resident CD3+, IL23R+ cells within eye will be informative with regard to the role of IL-23 in the uveitis.

Keywords: 432 autoimmune disease • 746 uveitis-clinical/animal model • 551 imaging/image analysis: non-clinical