Monocyte activation in patients with Wegener's granulomatosis

Abstract

Objective: Wegener's granulomatosis (WG) is an inflammatory disorder characterised by granulomatous inflammation, vasculitis, and necrotising vasculitis and is strongly associated with anti-neutrophil cytoplasmic antibodies (ANCA). Activated monocytes/macrophages are present in renal biopsy specimens and participate in granuloma formation by synthesising and secreting a variety of chemoattractants, growth factors, and cytokines. In view of these findings, in vivo monocyte activation was evaluated in patients with WG and the findings related to parameters of clinical disease activity.

Methods: Monocyte activation was analysed by measuring plasma concentrations of soluble products of monocyte activation, that is neopterin and interleukin 6 (IL6), by ELISA, and by quantitating the surface expression of activation markers on circulating monocytes by flow cytometry.

Results: Twenty-four patients with active WG were included in this study. Ten of these patients were also analysed at the time of remission. Twelve patients with sepsis served as positive controls, and 10 healthy volunteers as negative controls for monocyte activation. Patients with active disease had increased monocyte activation compared with healthy controls as shown by increased concentrations of neopterin (p < 0.0001) and increased surface expression of CD11b (p < 0.05) and CD64 (p < 0.05). In those patients with increased concentrations of IL6 during active disease plasma concentrations of IL6 decreased during follow up when patients went into remission (p < 0.0001). In addition, neopterin (r = 0.37, r = 0.44), IL6 (r = 0.37, r = 0.60) and CD63 expression (r = 0.39, r = 0.45) correlated significantly with disease activity as measured by the Birmingham Vasculitis Activity Score and C reactive protein values, respectively. Compared with patients with sepsis, all markers of monocyte activation in patients with vasculitis were lower.

Conclusion: It is concluded that disease activity in WG correlates with the extent of activation of monocytes, compatible with their role in the pathophysiology of this disease.

Figure 1

Box and whisker plots indicating the overall range (error bars), 25-75% range (boxes), and median value (horizontal lines) of neopterin plasma concentrations in patients with WG (A: active disease, Q: quiescent disease) compared with concentrations in patients with sepsis (S) and healthy controls (C). * p < 0.05, ** p < 0.0001 compared with healthy controls, † p = 0.074 compared with quiescent disease.

Figure 2

(A) A dot blot of the plasma concentrations of IL6 in 24 patients with WG (A: active disease, open squares represent 12 patients with newly diagnosed disease, closed squares represent 12 patients with relapsing disease, Q: quiescent disease, 10 patients) compared with concentrations in 12 patients with sepsis (S) and healthy controls (C). (B) Paired observations of IL6 plasma concentrations in 10 patients with active and quiescent disease. p<0.0001.

Figure 3

(A) Box and whisker plots of the surface expression CD63 on monocytes from patients with WG (A: active disease, Q: quiescent disease) compared with the expression on cells from patients with sepsis (S) and healthy controls (C). † p = 0.0787, ** p < 0.0001 compared with healthy controls. (B) Box and whisker plots of the surface expression of CD11b on monocytes from patients with WG (A: active disease, Q: quiescent disease) compared with the expression on cells from patients with sepsis (S) and healthy controls (C). * p < 0.05, ** p < 0.0001 compared with healthy controls. (C) Box and whisker plots of the surface expression of CD64 on monocytes from patients with WG (A: active disease, Q: quiescent disease) compared with the expression on cells from patients with sepsis (S) and healthy controls (C). * p < 0.05 compared with healthy controls.

Figure 4

Flow cytometry histogram representing membrane expression of Pr3 and MPO and the negative control staining on monocytes from a patient with active WG and a healthy control. Cell count and the mean fluorescence intensity (MFI) are depicted on the y and x axes respectively.

Figure 5

Surface expression of CD63 on monocytes (expressed as expression index, see methods) correlate with disease activity as expressed by the BVAS score (A) or CRP values (B).