The chemokine receptor CCR7 mediates corneal antigen-presenting cell trafficking.
OBJECTIVE
Trafficking of corneal antigen-presenting cells (APC) to draining lymph nodes (LN) is critical in triggering immune responses. However, very little is known about the molecular regulation of this pathway. We investigated the expression and function of the chemokine receptor CCR7 in mediating corneal APC migration in inflammation.


METHODS
Expression of CCR7 and its ligands, CCL21 and CCL19, in the normal and inflamed corneas was analyzed by RT-PCR and immunofluorescence staining. The phenotype of CCR7-expressing cells was identified by double-staining with different cell surface markers. To trace the trafficking of APC to draining LN, we injected corneal grafts with Alexa488-conjugated ovalbumin (OVA) and transplanted to syngeneic recipients. CCR7 expression on the Alexa488-conjugated OVA+ cells in the ipsilateral draining LN was analyzed by flow cytometry. To determine the functional role of CCR7, we injected anti-CCL21 neutralizing antibody subconjunctivally after corneal transplantation and analyzed changes in numbers of OVA+ cells in the draining LN. Each experiment was repeated at least three times.


RESULTS
Both CCR7 and its ligand CCL21 were significantly upregulated in inflamed corneas as measured by RT-PCR and immunofluorescence staining. CCR7+ cells were detected especially in the corneal periphery near LYVE-1+ lymphatic vessels. CCR7+ cells were universally CD11b+CD11c+, and a majority were major histocompatibility complex class II positive, suggesting a monocytic dendritic cell lineage and a relative state of maturation. Forty-eight h after syngeneic transplantation with OVA-loaded grafts, CCR7 expression was detected on the OVA+ cells in both the host corneal beds and the draining LN. Local administration of anti-CCL21 led to a significant suppression in the flow of OVA+CD11c+ cells to the draining LN.


CONCLUSIONS
These data suggest that in inflammation, APC expressing CCR7 on their cell surface interact with CCL21 to facilitate their migration from the cornea to draining LN via afferent lymphatics.
Jin
Yiping
Y
Schepens Eye Research Institute and the Massachusetts Eye & Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA. yiping.jin@schepens.harvard.edu <yiping.jin@schepens.harvard.edu>
Shen
Linling
L
Chong
Eva-Marie
EM
Hamrah
Pedram
P
Zhang
Qiang
Q
Chen
Lu
L
Dana
M Reza
MR
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D000938:Antigen-Presenting Cells / Q000378:metabolism; D001854:Bone Marrow Cells / Q000473:pathology; D002454:Cell Differentiation; D002465:Cell Movement / Q000187:drug effects; D054421:Chemokine CCL21; D019742:Chemokines, CC / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D003315:Cornea / Q000378:metabolism* / Q000473:pathology*; D003319:Corneal Stroma / Q000378:metabolism; D016039:Corneal Transplantation; D003713:Dendritic Cells / Q000378:metabolism / Q000473:pathology; D066298:In Vitro Techniques; D007267:Injections; D007634:Keratitis / Q000209:etiology / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D008198:Lymph Nodes; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010047:Ovalbumin / Q000008:administration & dosage / Q000378:metabolism; D054400:Receptors, CCR7; D019707:Receptors, Chemokine / Q000378:metabolism*; D013537:Sutures; D015854:Up-Regulation
D000906:Antibodies; C515479:Ccl21c protein, mouse; C515371:Ccr7 protein, mouse; D054421:Chemokine CCL21; D019742:Chemokines, CC; D054400:Receptors, CCR7; D019707:Receptors, Chemokine; D010047:Ovalbumin