CD40 ligand as a potential biomarker for atherosclerotic instability.

OBJECTIVE: The signaling protein CD40 and its ligand, CD40L, are thought to contribute to atherosclerotic plaque formation and rupture. We sought to determine their utility as markers of cerebral atherosclerosis and neurological dysfunction.
METHODS: We recruited 82 patients with acute cerebral infarction (ACI) and classified each as having large-artery atherosclerosis (LAA, 30), small-artery occlusion (36), or cardioaortic embolism (16). We also recruited 17 patients who had carotid artery stenosis (CAS) without stroke and 20 healthy individuals as controls. CD40L expression on peripheral blood monocytes (PBMCs) was detected by direct immunofluorescence with flow cytometry, and serum soluble CD40L (sCD40L) was measured by ELISA.
RESULTS: CD40L expression on PBMCs was highest in the LAA group, followed by that in the CAS group (both P < 0·01 versus control). It was also higher in patients with atherosclerotic infarction than in those without atherosclerosis (P < 0·05). PBMC CD40L expression was sensitive and specific for detecting atherosclerosis and LAA cerebral infarction and was superior to serum C-reactive protein for predicting cerebral atherosclerosis (P < 0·01). Serum sCD40L was higher in patients with ACI than in healthy controls (P < 0·01) or patients with CAS (P < 0·01) and correlated with increased disability on three scales (all P < 0·01).
CONCLUSIONS: We conclude that patients with ACI have an upregulated CD40-CD40L system, which could be used as a clinical biomarker for assessing atherosclerotic instability and severity of neurological dysfunction.