BS32 Evaluating the expression and role of chemokine receptors in CD4+CD28null T cells from patients with acute coronary syndrome

Rationale Chemokines and their receptors have important roles in dysregulated leukocyte migration which drives Acute Coronary Syndrome (ACS). CD4+CD28null (CD28null) T lymphocytes are unique T cells which expand in a subgroup of ACS patients. CD28null T cells are preferentially identified in unstable atherosclerotic plaques but the mechanisms regulating their migration are yet to be explained. The aim of this project was to characterise chemokine receptors which may regulate CD28null T cell migration and function. Methods Fresh whole blood from ACS patients was used to quantify the expression of chemokine receptors in CD28null and CD4+CD28+ (CD28+) T cells using flow cytometry. Transwell chemotaxis assays and flow adhesion assays using sorted CD4+ T cells from ACS patients were performed to assess the role of chemokine receptors in cell capture and migration. Flow cytometry was used to assess the effector functions (production of inflammatory cytokines, cytolytic molecules and degranulation) of CD28null T cell following chemokine stimulation. Results Chemokine receptor expression was significantly higher in CD28null T cells compared to CD28+ T cells. CD4+ T cells with an expansion of CD28null T cells adhered to immobilised fractalkine (CX3CL1) in flow adhesion assays. However, CD4+ T cells without an expansion of CD28null T cells did not adhere to immobilised CX3CL1. Ongoing experiments are investigating CD28null T cell migration towards chemokines and effector T cell function in response to chemokine stimulation. Conclusions Chemokine receptor expression is upregulated in CD28null T cells compared to CD28+ T cells. Of note, CX3CR1 is preferentially expressed by CD28null T cells. Only CD4+ T cells from ACS patients with an expansion of CD28null T cells adhere to immobilised CX3CL1. Current work is evaluating whether chemokine stimulation alters the effector functions of CD28null T cells Conflict of Interest None