T helper type 1 lymphocytes drive inflammation in human atherosclerotic lesions

Abstract

Atherosclerotic lesions are infiltrated by macrophages and T lymphocytes, potentially reactive to pathogens. We studied in vivo activated T lymphocytes that infiltrate atherosclerotic plaques of Helicobacter pylori-infected patients with or without anti-Chlamydia pneumoniae antibodies. In all atherosclerotic lesions, T helper type 1 (Th1) cells were predominant. C. pneumoniae-specific T cells were detected only in the plaques of anti-C. pneumoniae seropositive patients, whereas H. pylori-specific T cells were found in the gastric mucosa but not in the plaques of the same patients. Plaque-derived Th1 cells expressed cytotoxicity, proapoptotic activity, and help for monocyte tissue factor production. Although multifactorial, atherosclerosis can be regarded as a Th1-driven immunopathological condition.

Fig. 1.

Cytokine profile of the T cell clones derived from atherosclerotic plaques. Plaque-derived T cell clones were obtained from 10 H. pylori-infected patients, five of whom (A–E) were seropositive for anti-C. pneumoniae antibodies, whereas the other five (F–K) were seronegative. Duplicate samples of supernatants of mitogen-stimulated T cell clones were assayed for cytokine production. CD4⁺ and CD8⁺ clones able to produce IFN-γ, but not IL-4, were categorized as Thl and Tc1, whereas CD4⁺ and CD8⁺ clones producing both IFN-γ and IL-4 were coded as Th0 and Tc0, respectively.

Fig. 2.

Antigen repertoire of plaque-infiltrating T cell clones reactive to C. pneumoniae. Th1 and Th0 clones were tested for proliferation to C. pneumoniae EB (Cp EB), recombinant C. pneumoniae HSP-60, HSP-10, and OMP-2 in the presence of irradiated autologous APCs.

Fig. 3.

C. pneumoniae antigen-induced cytokine production by plaque-infiltrating T cell clones. C. pneumoniae-specific Th1 or Th0 clones were stimulated with the appropriate antigen, and IFN-γ, TNF-α, IL-4, and IL-5 production was measured in culture supernatants. In unstimulated control cultures, levels of IFN-γ, TNF-α, IL-4, and IL-5 were consistently <0.05 ng/ml.

Fig. 4.

Cytotoxic and proapoptotic activity of C. pneumoniae-specific plaque-infiltrating T cells. (A) To assess their perforin-mediated cytotoxicity, C. pneumoniae-specific T cell clones were cocultured at different effector-to-target ratios with ⁵¹Cr-labeled autologous EBV-B cells pulsed with C. pneumoniae EB (▴) or H. pylori lysate (▵), and ⁵¹Cr release was measured as index of specific target cell lysis. (B) To assess their ability to induce apoptosis in target cells, C. pneumoniae-specific T cell clones stimulated with mitogen (▪) or medium alone (□) were cocultured with ⁵¹Cr-labeled Fas⁺ Jurkat cells, and ⁵¹Cr release was measured as index of apoptotic target cell death. Data of three representative clones are reported.

Fig. 5.

C. pneumoniae-specific T cells induce TF production by monocytes. To assess their ability to induce TF production by monocytes, C. pneumoniae-specific Th1 and Th0 clones were cocultured with autologous monocytes in the presence of medium or C. pneumoniae EB, and TF production by monocytes was assessed by an appropriate ELISA.