Expanded CD14^hiCD16^- Immunosuppressive Monocytes Predict Disease Severity in Patients with Acute Pancreatitis

Mild acute pancreatitis (AP) is a self-limiting disease, whereas severe AP has high mortality because of enhanced systemic inflammation and multiple organ failure. In experimental models of AP, infiltration of monocytes and activation of monocyte-derived macrophages largely determine the severity of the disease. Our previous studies have shown that CD11b⁺Ly-6C^hi inflammatory monocytes were mobilized from bone marrow into peripheral blood and inflamed pancreas during the early stage of AP. However, the phenotype and characteristics of circulating monocytes in patients with AP are not well defined. Fifty patients with AP and nine age- and sex-matched healthy volunteers were enrolled in this study. Compared with those of healthy volunteers, the proportion of CD14^hiCD16^- monocytes and the level of myeloid-related cytokines/chemokines were increased in AP patients within 48 h after disease onset, especially in patients with a severe disease course. Moreover, the increased monocyte proportions were associated with decreased HLA-DR expression and a reduced T cell count. Notably, dynamic changes in circulating CD14^hiCD16^- monocytes and their HLA-DR expression, as well as in CD4⁺ T cells, were obviously different between moderate severe AP and severe AP. Last, area under the receiver operating characteristic analysis showed that the combination of CD14^hiCD16^- monocyte proportions with their HLA-DR level had higher accuracy for predicting the severity of AP. Taken together, the ratio of CD14^hiCD16^- monocytes and their HLA-DR level might assist in predicting the severity of disease in AP patients at admission and in monitoring patients' clinical status during recovery.