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.