Objective—The T-cell receptor zeta (TCR)-chain is a master sensor and regulator of lymphocyte responses. Loss of TCR-chain expression has been documented during infectious and inflammatory diseases and defines a population of effector T cells (TCR^Dim T cells) that migrate to inflamed tissues. We assessed the expression and functional correlates of circulating TCR^Dim T cells in coronary artery disease.

Methods and Results—We examined the expression of TCR-chain by flow cytometry in 140 subjects. Increased peripheral blood CD4⁺ TCR^dim T cells were found in patients with acute coronary syndromes (ACS, n=66; median 5.3%, interquartile 2.6 to 9.1% of total CD4⁺ T cells; P<0.0001) compared to chronic stable angina (CSA, n=32; 1.6%; 1.0 to 4.1%) and controls (n=42; 1.5%; 0.5 to 2.9%). Such increase was significantly greater in ACS patients with elevated levels of C-reactive protein, and it persisted after the acute event. Moreover, TCR^dim cells were also more represented within CD8⁺ T cell, NK, and CD4⁺CD28^null T cell subsets in ACS compared to CSA and controls. Finally, CD4⁺ and CD8⁺ TCR^Dim T cells isolated from ACS displayed an enhanced transendothelial migratory capacity.

Conclusions—TCR^dim T cells, an effector T-cell subset with transendothelial migratory ability, are increased in ACS, and may be implicated in coronary instability.