Interleukin 12 induces T-cell recruitment into the atherosclerotic plaque

CD4 T cells, through the release of cytokines as well as direct effector functions, have been implicated in promoting inflammation of the atherosclerotic plaque. Plaque-infiltrating CD4 T cells include a specialized subset of CD4⁺CD28^- T cells that express a unique profile of regulatory receptors and are responsive to novel microenvironmental cues. Here we report that CD4⁺CD28^- T cells, either isolated from the plaque tissue or from the blood of patients with acute coronary syndrome (ACS), spontaneously express interleukin (IL)-12 receptors, even in the absence of antigenic stimulation. CD4⁺CD28^- IL-12R⁺ cells responded to IL-12 stimulation with the upregulation of the chemokine receptor CCR5 and the C-type lectin receptor CD161, both implicated in regulating tissue homing of effector T cells. IL-12 treatment of CD4⁺CD28^- T cells enhanced their chemotaxis and transendothelial migration toward the chemokine CCL5. In vivo relevance for the role of IL-12 in regulating the recruitment of CD4⁺CD28^- T cells into the atheroma was examined in human atheroma-SCID mouse chimeras. Exposure of nonstimulated CD4⁺CD28^- T cells to IL-12 was sufficient to amplify T-cell accumulation within the inflamed plaque, and coadministration of anti-CCR5 antibodies blocked T-cell recruitment into the plaque. Thus, CD4 ⁺CD28^- T cells functionally resemble NK cells, which have proinflammatory activity even in the unprimed state and respond to any IL-12-inducing host infection with a shift in tissue trafficking and accrual in inflammatory lesions.