C Reactive Protein and Enzymatically Modified LDL Cooperatively Promote Dendritic Cell-mediated T Cell Activation

Background: Enzymatically modified low density lipoprotein (eLDL), C reactive protein (CRP), dendritic cells (DCs), and T cells were shown to be involved in the pathogenesis of atherosclerosis. This study aimed to investigate whether eLDL and CRP could cooperatively promote DC-mediated T cell activation and proliferation.

Method: Low density lipoprotein was isolated from healthy human plasma and treated with proteases and cholesterol esterase. CD14 monocytes were isolated from human peripheral blood by gradient centrifugation and enriched with CD14 Microbeads, which were then induced with recombinant human IL-4 and granulocyte-macrophage colony-stimulating factor before treated with eLDL and/or CRP. DC differentiation was assessed by flow cytometry. T cell activation was induced by coculture of peripheral blood mononuclear cells with autologous DCs. T cell proliferation was monitored by Carboxyfluorescein succinimidyl ester weak and CD3 positive. Cytokine production was analyzed by enzyme-linked immunosorbent assay and gene expression by quantitative polymerase chain reaction.

Results: CRP and eLDL promoted monocytic DC differentiation individually and cooperatively evidenced by the increase of CD11b, CD13, CD40, CD80 and CD86 positive cells. Accordingly, the production of IL-12 and TNF-α was significantly increased by CRP and/or eLDL treatment. CRP and eLDL-treated DCs elicited strong Th1 reaction and T cell proliferation.

Conclusions: CRP and eLDL additively promoted DC maturation/activation and DC-mediated T cell activation and Th1 responses.