Abstract 11512: Increased Cytolytic Activity By CD8+ T Cells From Apob-100 Related-Peptide Immunized Mice is Specific to Lipid-Associated Antigens
Background: We have previously reported that immunization with apoB-100 related-peptide p210 significantly reduces atherosclerosis and decreases intra-plaque CD11c+ dendritic cells (DCs) in apoE-/- mice. Adoptive transfer experiments showed that athero-protection was mediated by CD8+ T cells. Because apoB-100 is found on the LDL fraction of serum lipids, we assessed the CD8+ T cell cytolytic activity of p210 immunized mice specific to lipid-associated antigens presented by DCs.
Methods and Results: ApoE-/- mice were immunized at 7, 9, and 12 weeks of age with p210/cBSA/alum, cBSA/alum, or PBS. One week after the third immunization, mice were euthanized to collect spleen CD8+ T cells. Bone-marrow derived DCs were differentiated from naïve apoE-/- mice and used as target cells. A four-hour lytic assay was performed using a CD8-to-DC ratio of 3:1 in culture medium with 10% FBS. The cells were then collected and stained for CD11c to identify DCs and 7-AAD to assess cell lysis using flow cytometry. There was significantly more lytic activity by CD8+ T cells from p210/cBSA/alum immunized mice compared to cBSA/alum and PBS (Table). When the assay was performed in media with delipidated FBS, the lytic activity specific to CD8+ T cells from from p210/cBSA/alum immunized mice was abrogated (Table), suggesting that the lipid fraction of FBS in the culture media provided a source of antigen. Loading of DCs with FITC-labeled p210 24 hours prior to the lytic assay demonstrated antigen uptake and specificity of the lytic activity of CD8+ T cells from p210/cBSA/alum immunized mice (Table).
Conclusion: Our results show that the cytolytic function of CD8+ T cells targeting DCs are specific to lipid-associated antigens, specifically the p210 fragment of apoB-100, and this may underly the protective effects of p210 immunization.
- © 2011 by American Heart Association, Inc.