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.