Differential pathways govern CD4+ CD28- T cell proinflammatory and effector responses in patients with coronary artery disease.

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-gamma 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-gamma 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.

Heat-shock protein 60-reactive CD4+CD28null T cells in patients with acute coronary syndromes.

BACKGROUND: CD4+CD28null T cells are present in increased numbers in the peripheral blood of patients with acute coronary syndrome (ACS) compared with patients with chronic stable angina (CSA). The triggers of activation and expansion of these cells to date remain unclear. METHODS AND RESULTS: Twenty-one patients with ACS and 12 CSA patients with angiographically confirmed coronary artery disease and 9 healthy volunteers were investigated. Peripheral blood leukocytes were stimulated with human cytomegalovirus (HCMV), Chlamydia pneumoniae, human heat-shock protein 60 (hHSP60), or oxidized LDL (ox-LDL). CD4+CD28null cells were separated by flow cytometry and assessed for antigen recognition using upregulation of interferon-gamma and perforin mRNA transcription as criteria for activation. CD4+CD28null cells from 12 of 21 patients with ACS reacted with hHSP60. No response was detected to HCMV, C pneumoniae, or ox-LDL. Incubation of the cells with anti-MHC class II and anti-CD4 antibodies but not anti-class I antibodies blocked antigen presentation, confirming recognition of the hHSP60 to be via the MHC class II pathway. Patients with CSA had low numbers of CD4+CD28null cells. These cells were nonreactive to any of the antigens used. Circulating CD4+CD28null cells were present in 5 of the 9 healthy controls. None reacted with hHSP60. CONCLUSIONS: We have shown that hHSP60 is an antigen recognized by CD4+CD28null T cells of ACS patients. Endothelial cells express hHSP60 either constitutively or under stress conditions. Circulating hHSP60-specific CD4+CD28null cells may, along other inflammatory mechanisms, contribute to vascular damage in these patients.

Placental infection with Chlamydia pneumoniae and intrauterine growth restriction.

BACKGROUND: The concept that low birth weight infants are more predisposed to coronary artery disease (CAD) in adulthood has been studied extensively. Although many infectious agents have been associated with intrauterine growth restriction (IUGR), Chlamydia pneumoniae an organism implicated in CAD has not been investigated. It was our aim to assess whether C. pneumoniae DNA is present in placental tissue and whether its detection is associated with IUGR. METHODS: Fifty-nine pregnant women were studied: 32 women had an uncomplicated pregnancy with no antenatal or post-natal evidence of IUGR. Twenty-seven women had pregnancies with ultrasonographically demonstrated IUGR, defined as foetal abdominal circumference measuring less than 2 S.D.s from the mean for gestational age. At the time of delivery, maternal blood and placental tissue samples were obtained. Placental samples were taken from four sites centrally and peripherally on the maternal and foetal side of the placentas and tested by nested polymerase chain reaction for C. pneumoniae DNA. IgG antibodies to C. pneumoniae were measured using microimmunfluorescence. RESULTS: C. pneumoniae DNA was detected in 44% of the placental tissue but there was no difference in the prevalence of bacterial DNA between the control and the low birth weight group (P=0.58). Additionally C. pneumoniae seropositivity did not differ between the index and control groups (78 vs. 70%, P=0.44). CONCLUSIONS: C. pneumoniae is present in placental tissue. Its presence however does not correlate with IUGR. Similarly, maternal C. pneumoniae seropositivity is not related to low birth weight. Thus C. pneumoniae infection is unlikely to play a role in the pathogenesis of IUGR.