Blocking of CCR7 by CCL19-IgG Reduces Migration of Mature Corneal Dendritic Cells to Draining Lymph Nodes

Abstract

Purpose: : The chemokine receptor CCR7 is essential for migration of mature dendritic cells to the regional lymph nodes. Recently it has been shown that blocking of CCR7 improves graft survival after allogeneic kidney and heart transplantation. Aim of this study was to evaluate whether blocking of CCR7 reduces migration of mature dendritic cells from the cornea to the draining lymph nodes and whether this leads to an improved graft survival in the murine model of low-risk keratoplasty.

Methods: : Pellets containing Freund's adjuvants and bovine serum albumin (BSA) conjugated to Alexa Fluor®488 fluorescent dye were placed into the corneal stroma of 6-8 weeks old BALB/c mice and treated by local administration of a CCR7 blocking fusion protein that consisted of CCL19 fused to the Fc part of human IgG1 (CCL19-IgG; 300 µg/ml). After 48 hrs cells of the draining lymph nodes were isolated, stained for CD11c and analyzed by flow cytometry. To test the effect of CCR7-blocking on graft rejection after allogeneic low-risk keratoplasty, corneal transplantation was performed using C57Bl/6-mice as donors and BALB/c-mice as recipients. Mice of the treatment group (n=13) received two intraperitioneal loading doses of CCL19-IgG (150µg) one day prior to transplantation followed by CCL19-IgG eye drops (300 µg/ml) twice a day for two weeks. All control mice received the same dose of control IgG.

Results: : In vivo fluorescence microscopy showed the uptake of Alexa 488-conjugated BSA by dendritic cells. Flow cytometry of the cells from the draining lymph nodes revealed that two days after pellet implantation 2.87 + 1.3 % of the cells CD11c+ were FITC+ (p<0.005 compared with cells from untreated mice). This effect was reduced after topical administration of CCL19-IgG (1.5 + 0.8 %; p<0.04). Survival proportions after keratoplasty were 76 % in the treatment group and 38 % in the control group 8 weeks after transplantation (p<0.05).

Conclusions: : Migration of activated corneal dendritic cells into the draining lymph nodes can be reduced by blocking of CCR7. This might offer a new treatment option in preventing graft rejection after keratoplasty.

Keywords: cytokines/chemokines • cornea: basic science • transplantation