Abstract 51: The Role of CCL5 in T cell Recruitment to the Aorta

Abstract

Introduction T cell adaptive immunity is involved in the pathogenesis of atherosclerosis. Previously our lab found that antigen presenting cells (APCs) present antigens to effector T cells (Teff). This causes local T cell activation and cytokine production, which sustain local inflammation. However, the chemokine(s) that drive T cell recruitment into the atherosclerotic aorta are not known. By multi-color flow cytometry to analyze chemokine receptor expression on T cells from Apoe-/- aorta, we found that more than 60% of CD4+ T cells in Apoe-/- aorta express CCR5. I hypothesize that CCR5 plays an important role in T cell recruitment to atherosclerotic aortas. Methods T cells in the aorta of Apoe-/- mice that have been on western diet (WD) for > 3 months were analyzed by multi-color flow cytometry by staining T cell markers and chemokine receptors (CCR7, CCR5, CXCR3, CXCR6, CCR6). 400,000 Teff cells from CD45.1 Apoe-/- mice were sorted and incubated with explanted Apoe-/- aortas 12 to 18 hrs with media alone, CCL-5 (one of the ligands of CCR5) neutralizing antibody (0.5 ug/ml) or PTX (300ng/ml). Afterward, T cell infiltration into aorta was quantified by FACS. To monitor T cell-APC interaction, effector T cells from Apoe-/- mice were labeled with fluorescent dye SNARF before incubation with aortas from Apoe-/- CD11c-YFP+ mice in the above 3 conditions. Aortas were imaged by 2 photon imaging. Results There is a significant increase of CCR5+ T cells (63±4% of TCRβ+ T cells) in the aorta of Apoe-/- WD mice vs. Apoe-/- on chow diet (9±8%, p<0.05) or WT (13±8%, p<0.05) (n=3 in each group). CCL5 neutralizing antibody significantly decreased the number of T cells infiltrating into aorta from 997±74 (CD45.1 T cell count in the arota)(media alone) to 652±165 (P<0.05, media alone vs. α-CCL5), and PTX further decreased this number to 456±98 (p<0.05, media alone vs. PTX)(n=3 in each group). 2 photon imaging showed that T cells infiltrated into adventitia of Apoe-/- aorta and were co-localized with DCs in the aorta. Neutralizing CCL5 inhibited T cell infiltration and remaining T cells were localized mostly outside of the adventitia. Conclusion CCL5 plays a role in Teff recruitment into the aorta. This suggests that targeting CCR5 or its ligand CCL5 may be effective to treat atherosclerosis.