Elevated plasma interleukin 34 levels correlate with disease severity-reflecting parameters of patients with haemorrhagic fever with renal syndrome.

Haemorrhagic fever with renal syndrome (HFRS) is characterized by an uncontrolled cytokine storm that causes vascular leakage and kidney injury. The cytokine interleukin 34 (IL-34) enhances proliferation and differentiation of myeloid cells and secretion of pro-inflammatory cytokines, which is involved in the pathogenesis of some inflammatory and infectious diseases, including acute kidney injury. To date, however, the role of IL-34 in patients with HFRS is unclear. This study aims to determine the plasma IL-34 levels of HFRS patients and discuss the possible effects of IL-34 in the pathogenesis of HFRS. Plasma levels of IL-34 in 52 HFRS patients and 20 healthy controls were quantified using enzyme-linked immunosorbent assay. Compared with healthy controls, the plasma IL-34 levels in HFRS patients were significantly elevated in acute phase [37.92 (0-215.45) pg/ml vs. 7.13 (0-19.44) pg/ml,  < .0001], and then decreased to the normal levels in convalescent phase. Importantly, IL-34 levels correlated positively with white blood cell counts and mononuclear cell counts ( = 0.592,  < .0001 and  = 0.458,  < .0001, respectively), and correlated negatively with platelet counts and serum albumin levels ( = -0.430,  < .0001 and  = -0.479,  = .0001, respectively). Plasma levels of IL-34 in HFRS patients were significantly elevated in acute phase and correlated with disease severity-reflecting parameters, which suggests a potential role of IL-34 in HFRS and should be future explored.