Non-classical and intermediate monocytes in patients following venous thromboembolism: Links with inflammation.

Background: Monocyte subsets are involved in atherosclerotic vascular disease and its thromboembolic complications. Moreover, the role of monocytes has been suggested in the pathogenesis of venous thromboembolism (VTE).

Objectives: We hypothesized that pro-inflammatory non-classical and intermediate monocytes are increased in the first months following VTE.

Material And Methods: We enrolled 70 patients aged 18-65 years (mean age 41.6 ±11.6) with the firstever provoked (n = 32; 45.7%) or unprovoked (n = 38; 54.28%) VTE episode, and 46 healthy controls. The exclusion criteria were: acute infection, cancer, autoimmune disorders, previous myocardial infarction (MI), or stroke. Monocyte subsets were assessed 12 (8.5-21.5) months after VTE using flow cytometry and were defined as classical (CD14++CD16-), intermediate (CD14++CD16+) and non-classical (CD14+CD16++).

Results: Patients with VTE had higher intermediate and non-classical monocyte counts compared to the control group (16.8 ±9.3 vs 10.4 ±4.0 cells/μL, and 64.1 ±25.2 vs 44.1 ±19.2 cells/μL, respectively, both p < 0.001). Increased non-classical monocyte counts were observed in patients who experienced a VTE incident within 12 months prior to enrollment (71.5 ±27.4 vs 56.03 ±20.6 cells/μL; p = 0.01) and those with unprovoked VTE (70.2 ±4.1 vs 58.8 ±4.3 cells/μL; p = 0.06). There were no differences in monocyte subsets related to the current anticoagulation.

Conclusions: Our data has shown for the first time that VTE is associated with an increased number of nonclassical and intermediate monocytes, which may indicate the involvement of monocyte-related mechanisms in the pathophysiology of this disease.