Abstract
Purpose :
Experimental Autoimmune Uveitis (EAU) and Primed Mycobacterial Uveitis (PMU) are two models of uveitis that have demonstrated mechanistic differences by histology, cytokine, and proteomic analysis. We sought here to compare the intraocular effector cells present on the day of peak inflammation using flow cytometry.
Methods :
EAU and PMU were initiated in female Lewis rats (total=16, EAU=5, PMU=11). Aqueous humor was collected on day 14 for EAU and on day 2 for PMU (days of peak inflammation). Eyes were analyzed individually. Cell surface labelling was performed for CD3, CD4, CD8, CD45R, and CD11b. Viability was established by dye exclusion. Flow cytometry data was collected on a CANTO II and analyzed with FlowJo. Populations were compared using Student’s t-test with Bonferroni correction (p<0.008 for significance).
Results :
Between 10 and 15 microliters of aqueous humor was obtained from each eye. The average cell concentration was 1.47x10^6 cells/ml for EAU eyes and 1.28 x 10^6 cells/ml for PMU eyes. There were two distinct populations defined by side scatter (SSC-A). 89% of the PMU cell population demonstrated high SSC-A compared to only 46% of the EAU population. CD3, CD45, CD11b, and CD8 cell surface markers also identified significantly different population by percentage in each model. CD3+ cells made up 5% of the PMU vs 24% of the EAU population (p=0.0001). CD45+ cells made up 4% of the PMU vs 19% of the EAU populations (p<0.0001). CD11b+ cells made up 53% of the PMU population and 30% of the EAU population (p=0.002). There was no significant difference in the percentage of CD3+CD4+ cells (78% in PMU and 71% in EAU, p=0.02). However, there was a significantly larger percentage of CD3+CD8+ cells in EAU (21%) vs PMU (7%) (p<0.0001).
Conclusions :
There are significant differences in the effector cell infiltrate found in the eyes of rats with PMU and EAU. PMU has more granulocytes and CD11b+ cells consistent with a predominantly innate immune effector cell response. EAU has a predominant small lymphocytic infiltrate with a significant T and B cell presence consistent with an adaptive immune driven response. The differences identified here continue to highlight the mechanistic differences between PMU and EAU, and support PMU as an alternative model to EAU.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.