258 - The low density lipoprotein receptor (LDLR) is crucial for the activation of CD8+ Tcells (ID 1204)
Abstract
Background and Aims
Cholesterol is essential for immune cell homeostasis. We evaluated the role cellular cholesterol acquired via the LDLR pathway on Tcell biology.
Methods
Immunophenotypic characterization of T cells from WT and LDLR KO mice was performed in vitro (anti-CD3/CD28) and in vivo (vaccination, homeostatic proliferation in Rag2 KO mice adoptively transferred with Tcells from LDL-R KO and WT mice). In parallel, T cells from FH patients with LDLR mutations were tested.
Results
LDLR expression increased after in vitro activation of CD8+ Tcells and its deficiency mainly affected CD8+ proliferation (-35%, p<0.01) paralleled by a reduction in INFγ production (-39.6%,p<0.01). In vivo antigen-specific activation (vaccination with ovalbumin), but not homeostatic proliferation, resulted in a decreased proliferation and cytokines production (↓IFNγ p<0.001, ↓IL13 p<0.01, ↓perforin p<0.05) in CD8+ of KO mice together with reduced expression of CD69 (-32%,p<0.01) and decreased AKT phosphorylation, a downstream molecule of the TCR. These defects were associated to significant reduction of neutral lipids and lipid rafts staining suggesting an altered lipid rafts distribution in KO CD8+ Tcells. Of note, memory CD8 Tcells from FH patients presented a decreased granzyme production when tested in vitro.
Conclusions
LDLR plays a critical role in regulating the immunometabolic responses in CD8+ Tcells, and thus might represent a checkpoint linking cellular cholesterol metabolism to adaptive immune response.
