Circulating and intraplaque interleukin-40 is associated with CTA-defined high-risk carotid plaques: an integrated imaging, serological, and histopathological study

Risk assessment of carotid atherosclerosis is moving beyond stenosis-based evaluation toward the identification of biologically active plaque phenotypes. Although CTA can characterize high-risk plaque morphology, biomarkers that reflect the inflammatory processes underlying these imaging features remain insufficiently defined. This study investigated whether circulating and intraplaque interleukin-40 (IL-40), a recently described immune mediator, is associated with CTA-defined high-risk carotid plaques and their histopathological features. This single-center retrospective observational study included 62 patients with carotid atherosclerotic stenosis who underwent carotid endarterectomy (CEA). Based on preoperative CTA features and a modified Plaque-RADS-based framework, patients were classified into low-risk plaque ( n = 28) and high-risk plaque ( n = 34) groups. CTA-derived parameters, including luminal stenosis, calcification volume and lipid-rich necrotic core (LRNC) volume were quantitatively assessed. Serum IL-40, monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-α (TNF-α) levels were measured preoperatively and on postoperative day 7. CEA specimens were evaluated using hematoxylin and eosin staining and immunohistochemistry for CD68, α-smooth muscle actin (α-SMA), and IL-40. Logistic regression and receiver operating characteristic analyses were performed to assess factors associated with high-risk plaques. Baseline clinical characteristics were comparable between high-risk and low-risk groups. As expected given that LRNC/low-attenuation plaque burden contributed to the imaging-based classification framework, LRNC volume was greater in the high-risk plaque group than in the low-risk plaque group (47.21 ± 8.36 mm³ vs. 35.00 ± 8.01 mm³, P < 0.001), whereas luminal stenosis and calcification volume did not differ significantly. Preoperative serum IL-40, MCP-1, and TNF-α levels were higher in patients with high-risk plaques than in those with low-risk plaques, and levels of all three cytokines were lower on postoperative day 7 than preoperatively. Serum IL-40 positively correlated with LRNC burden ( r = 0.74, P < 0.001). In exploratory multivariable logistic regression, higher IL-40 (OR = 1.30, 95% CI, 1.10–1.54, P = 0.002), MCP-1 (OR = 1.23, 95% CI, 1.05–1.44, P = 0.010), and TNF-α (OR = 1.17, 95% CI, 1.01–1.36, P = 0.039) levels remained associated with high-risk plaque status. Histopathological analysis showed larger necrotic cores, greater CD68-positive macrophage infiltration, and stronger IL-40 expression in high-risk plaques. A combined model incorporating IL-40, MCP-1, and TNF-α achieved an area under the curve of 0.84 (95% CI, 0.74–0.94). IL-40 may provide complementary biological information alongside CTA-based plaque characterization and established inflammatory markers and warrants further evaluation in larger prospective cohorts.