No abstract

Although exogeneous “danger” signals such as LPS can activate APC to produce a Th1 response, the nature of events initiating a Th2 response is controversial. We now show that pathogen-derived products have the capacity to induce bone marrow-derived dendritic cell cultures to acquire a phenotype that promotes the differentiation of naive CD4+ T cells toward either a Th1 or Th2 phenotype. Thus, LPS-matured dendritic cells (DC1) promote a Th1 response (increased generation of IFN-γ and reduced production of IL-4) by Ag-stimulated CD4+ T cells from the DO.11.10 transgenic mouse expressing a TCR specific for an OVA peptide (OVA323–339). In contrast, a phosphorylcholine-containing glycoprotein, ES-62, secreted by the filarial nematode, Acanthocheilonema viteae, which generates a Th2 Ab response in vivo, is found to induce the maturation of dendritic cells (DC2) with the capacity to induce Th2 responses (increased IL-4 and decreased IFN-γ). In addition, we show that the switch to either Th1 or Th2 responses is not effected by differential regulation through CD80 or CD86 and that a Th2 response is achieved in the presence of IL-12.

Background-CD4ϩ CD28 null 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 ϩ CD28 null cells were separated by flow cytometry and assessed for antigen recognition using upregulation of interferon-␥ and perforin mRNA transcription as criteria for activation. CD4ϩ CD28 null 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 ϩ CD28 null cells. These cells were nonreactive to any of the antigens used. Circulating CD4 ϩ CD28 null 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 CD4ϩ CD28 null T cells of ACS patients. Endothelial cells express hHSP60 either constitutively or under stress conditions. Circulating hHSP60-specific CD4 ϩ CD28 null cells may, along other inflammatory mechanisms, contribute to vascular damage in these patients.