Characterization of CD8(+)CD57(+) T cells in patients with acute myocardial infarction

Abstract

Although T cells are known to be involved in the pathogenesis of coronary artery disease, it is unclear which subpopulation of T cells contributes to pathogenesis in acute myocardial infarction (MI). We studied the immunological characteristics and clinical impact of CD8(+)CD57(+) T cells in acute MI patients. The frequency of CD57(+) cells among CD8(+) T cells was examined in peripheral blood sampled the morning after acute MI events. Interestingly, the frequency of CD57(+) cells in the CD8(+) T-cell population correlated with cardiovascular mortality 6 months after acute MI. The immunological characteristics of CD8(+)CD57(+) T cells were elucidated by surface immunophenotyping, intracellular cytokine staining and flow cytometry. Immunophenotyping revealed that the CD8(+)CD57(+) T cells were activated, senescent T cells with pro-inflammatory and tissue homing properties. Because a high frequency of CD8(+)CD57(+) T cells is associated with short-term cardiovascular mortality in acute MI patients, this specific subset of CD8(+) T cells might contribute to acute coronary events via their pro-inflammatory and high cytotoxic capacities. Identification of a pathogenic CD8(+) T-cell subset expressing CD57 may offer opportunities for the evaluation and management of acute MI.

Figure 1

The frequency of CD8⁺CD57⁺ T cells and short-term cardiovascular mortality in acute MI patients. The study population was divided into 48 cases of survival and seven cases of cardiovascular mortality, and the frequency of a specific T-cell population was compared between two patient groups. (a) Gating strategy. (b, c) The frequency of CD57⁺ cells (b) or CD28^null cells (c) among CD8⁺ T cells was compared between the two groups. (d, e) The frequency of CD57⁺ cells (d) or CD28^null cells (e) among CD4⁺ T cells was compared between the two groups. Data are expressed as the means±s.d. (f) Representative flow cytometry plots are presented for CD57 and CD28 expression in CD8⁺ T cells in patients who survived (left) and patients who suffered from cardiovascular mortality (right). (g) The patients (48 cases of survival and seven cases of cardiovascular mortality) were divided into two groups by median level (25%) of CD57⁺ T cell fraction in the CD8⁺ T-cell population. Kaplan-Meier plot shows that the 6-month survival rate was significantly lower in patients with CD8⁺CD57⁺ T cells ≥25% (dotted line) than in patients with CD8⁺CD57⁺ T cells <25% (solid line). *P<0.05. MI, myocardial infarction.

Figure 2

Immunophenotyping analysis of CD8⁺CD57⁺ T cells from acute MI patients. The MFI was compared for surface markers in both CD8⁺CD57⁺ and their paired CD8⁺CD57⁻ T cell populations (n=58). Cells were stained with monoclonal antibodies against markers indicating the recent activation of T cells, such as HLA-DR, PD-1 and FasL (a), markers for the senescence and memory status of T cells, such as CD28, IL-7Rα and CD45RO (b), natural killer cell-related proteins such as CD56, CD94 and NKG2D (c), tissue-homing markers such as CX3CR1 and CCR5 (d) and central-homing markers such as CCR7 and CD62L (e). The P value for each surface marker was calculated using the paired t-test. **P<0.01. MFI, mean fluorescent intensity; MI, myocardial infarction.

Figure 3

Functional reactivity of CD8⁺CD57⁺ T cells from acute MI patients. (a) PBMCs were stimulated with anti-CD3 antibody for 6 h, and intracellular cytokine staining for IFN-γ, TNF-α and IL-17A was performed (n=58). The frequency of IFN-γ-, TNF-α- or IL-17A-secreting cells in the CD8⁺CD57⁺ T-cell population was compared with those in the paired CD8⁺CD57⁻ T-cell population. (b) IFN-γ secretion by CD8⁺CD57⁺ T cells in response to IL-12 and IL-18 stimulation without anti-CD3 antibody for 48 h was examined (n=6). (c) Intracellular staining for cytotoxic granule proteins was performed (n=58). The frequency of granzyme A⁺, granzyme B⁺ or perforin⁺ cells in either the CD8⁺CD57⁺ or CD8⁺CD57⁻ T-cell populations was assessed by flow cytometry. The P value for each protein was calculated using the paired t-test. **P<0.01. MI, myocardial infarction; PBMC, peripheral blood mononuclear cell.