Differential Pathways Govern CD4+CD28− T Cell Proinflammatory and Effector Responses in Patients with Coronary Artery Disease

Abstract

Patients with acute coronary syndromes experience circulatory and intraplaque expansion of an aggressive and unusual CD4+ lymphocyte subpopulation lacking the CD28 receptor. These CD4+CD28− cells produce IFN-γ and perforin, and are thought to play an important role in coronary atheromatous plaque destabilization. Aberrant expression of killer Ig-like receptors (KIRs) in CD4+CD28− cells is broadly thought to be responsible for their cytotoxicity, but the mechanisms involved remain poorly defined. We therefore sought to investigate the mechanism and regulation of CD4+CD28− cell functionality using T cell clones (n = 536) established from patients with coronary artery disease (n = 12) and healthy volunteers (n = 3). Our functional studies demonstrated that KIR2DS2 specifically interacted with MHC class I-presenting human heat shock protein 60 (hHSP60) inducing cytotoxicity. Further investigations revealed the novel finding that hHSP60 stimulation of TCR alone could not induce a cytotoxic response, and that this response was specific and KIR dependent. Analysis of CD4+CD28−2DS2+ clones (n = 162) showed that not all were hHSP60 cytotoxic; albeit, their prevalence correlated with coronary disease status (p = 0.017). A higher proportion of clones responded to hHSP60 by IFN-γ compared with perforin (p = 0.008). In this study, for the first time, we define the differential regulatory pathways involved in CD4+CD28− cell proinflammatory and effector responses. We describe in this study that, contrary to previous reports, CD4+CD28− cell recognition and killing can be specific and discriminate. These results, in addition to contributing to the understanding of CD4+CD28− cell functionality, may have implications for the monitoring and management of coronary artery disease progression.