Distinct cytokine pattern in aqueous humor during immune reactions following penetrating keratoplasty

Abstract

Purpose: Cytokine patterns in the aqueous humor before penetrating keratoplasty might permit us to predict the development of immune reactions. We therefore analyzed ten different cytokines in the aqueous humor of patients before and following penetrating keratoplasty.

Methods: We collected aqueous humor from patients undergoing cataract extraction or penetrating keratoplasty (baseline, n=197), from patients undergoing cataract extraction after penetrating keratoplasty without signs of an endothelial immune reaction (acceptors, n=33), and from patients who underwent irrigation of the anterior chamber due to endothelial immune reactions (rejectors, n=25). We determined interleukin (IL)-1b, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, interferon (INF)-gamma, and tumor necrosis factor-alpha in the aqueous humor, using cytometric bead arrays.

Results: We found statistically significant differences for IL-10 and INF-gamma among the study groups. We observed no significant differences concerning all other cytokines evaluated in this study.

Conclusions: Elevated levels of INF-gamma emphasize its important role in immune reactions following penetrating keratoplasty. Antagonizing INF-gamma might be an option when treating immune reactions. High levels of IL-10 during endothelial immune reactions may reflect a downregulation of the delayed-type hypersensitivity. Perhaps this is a donor-specific activation of the immune privilege in the anterior chamber as an attempt to prevent damage during immune reactions. We plan to investigate, in upcoming prospective trials, whether the analysis of cytokine patterns in the aqueous humor before penetrating keratoplasty will enable us to predict the occurrence of immune reactions.

Figure 1

Random forest analysis demonstrates the relative importance of individual cytokines in classifying different study groups.Random forest analysis of data set 1 (A) and data set 2 (B) demonstrating the relative importance of individual cytokines in classifying aqueous humor from different study groups. The individual plots represent the relative importance of the cytokines in the overall classification. The vertical axes represent individual cytokines sorted by importance. The horizontal axes represent the average decrease in classification accuracy. Abbreviations: IL=interleukin, TNF=tumor necrosis factor, INF=interferon.

Figure 2

Box plot diagram shows the relative cytokine levels.Box plot of the relative cytokine levels on data set 1 (A; human inflammation kit) and data set 2 (B; Th-1/Th-2 kit). Relative cytokine levels were determined by dividing the individual cytokine level through the maximum cytokine level of that cytokine measured in the whole study group. After correction for multiple comparisons, the Kruskal–Wallis test revealed a statistically significant difference only for IL-10 in data set 1 and for INF-γ in data set 2 among the three study groups. The filled dots represent median values, the circles outliers, and the boxes 95% intervals. Abbreviations: IL=interleukin, TNF=tumor necrosis factor, INF=interferon.