Abstract 11: T Cell Functions in a Novel Antigen-specific Experimentally-induced Model of Atherosclerosis
Introduction While it is realized that inflammation plays a key role in the development of atherosclerosis, the underlying mechanism of how T cells, directly or indirectly, trigger and propagate the disease process, is not forthcoming. This is because there is no knowledge of what constitutes an atherogenic T cell and how to isolate it. New and innovative ideas are needed.
Hypothesis We reason that T cells are antigen specific and identification of the atherogenic antigenic epitopes of an autoantigen should lead us to identification of the atherogenic T cells themselves.
Methods Since the T cell receptor only recognizes a short peptide of the antigen in association with major histocompatibility complex (MHC) proteins, our focus was directed towards elucidating the peptides that form a ligand with MHC class II proteins and bind to atherogenic T cells. It has been known that oxidized low-density lipoprotein, ApoB100, heat-shock protein 60 and β2 glycoprotein I are the major atherogenic antigens. Because different MHC haplotypes have different binding motifs of peptide sequences and most atherosclerosis experiments are carried out in the H-2b ApoE-/- mice, we searched for H-2b binding motifs along the entire amino acid sequence of murine ApoB100 according to the prediction model of Liu et al. ApoE-/- mice fed Western diet (WD) for 8 weeks were immunized with the identified peptides in CFA. Mice were boosted in 2 weeks and 3 weeks later were sacrificed and the aortic trees were isolated. The extent of atherosclerosis was assessed via en face staining of the aortic samples with Oil Red O.
Results We identified eighteen such peptides, six of which were selected for synthesis. Two of the peptides, peptide6 (P6) and peptide3 (P3) induced strong proliferative responses in immunized mice, but only P6 was atherogenic in enhancing development of atherosclerosis in WD-fed and P6-immunized mice. The proliferative T cells were of the CD4 type, producing IL-17, IFNγ as well as IL-10 and IL-13. T cell clones were derived from P6-primed mice and adoptive transfer of these clones into WD-fed recipients also showed enhanced atherosclerosis.
Conclusions Our identification of a T cell epitope of ApoB100 allows cloning of a population of peptide-specific atherogenic T cells.
- © 2013 by American Heart Association, Inc.