Background/Purpose Systemic sclerosis (SSc) is characterised by microvascular damage, immune cell activation and fibrosis of the skin and internal organs. In SSc, the immune-inflammatory infiltrate is primarily made of macrophages and T cells (1). The alternatively activated macrophages (M2) are characterized by an increased expression of specific markers, primarily CD206 (macrophage mannose receptor-1) and macrophage scavenger receptors, and participate in the fibrotic process through the production of pro-fibrotic molecules (i.e. fibronectin, TGFβ) (2). The study investigated the presence of CD206⁺cells in the peripheral blood and skin of SSc patients. The capability of SSc serum to induce the expression of CD206 in peripheral blood mononuclear cells (PBMCs) of healthy subjects was also investigated.

Methods Eight SSc patients (mean age 65±7 years) who fulfilled the new criteria of EULAR/ACR (3) and five age matched healthy subjects (HS) were enrolled into the study, after signing of Informed Consent and local Ethical Committee approval. Peripheral blood from SSc patients and HS was analysed by flow cytometry (FC) to detect the presence of cells positive for CD206 and CD14 (a marker of monocyte/macrophage lineage). Skin biopsies were obtained from four of the enrolled SSc patients who were characterized by a “limited” cutaneous involvement (lSSc) and the five HS. The PBMCs obtained from the HS enrolled were plated into FlexPerm chamber slides (2×10⁶cells/spot) and maintained for 12 hours in growth medium at 10% of fetal bovine serum in order to isolate the monocyte/macrophage cells. These monocyte/macrophage cells were stimulated for 48 hours with serum from SSc patients and the HS themselves. The expression of CD206 and CD68 (a macrophage marker) was evaluated by immunohistochemistry (IHC) on skin biopsies and by immunocytochemistry (ICC) on cultured human monocyte/macrophages derived from PBMCs.

Results In the peripheral blood of SSc patients, the percentage of CD206⁺cells was significantly higher than that of the HS (p<0.01). The FC confirmed that the CD206⁺cells belong to the monocyte/macrophage lineage given the co-expression of CD14. In the skin of SSc patients, the CD206⁺cells were detected in the immune-inflammatory infiltrate which is characterized by the presence of macrophages (CD68⁺cells). Conversely, in the skin of HS no CD206⁺cells were observed. ICC showed that SSc serum stimulated PBMCs-derived monocyte/macrophage cells to express CD206 and also induced these cells to express CD68 thus indicating their activation into macrophages. Conversely, serum from HS was unable to stimulate the expression of CD206 in these cells.

Conclusion These preliminary results show the presence of CD206⁺cells in both peripheral blood and skin of SSc patients. Moreover, the ability of SSc serum to induce the expression of this M2 macrophage marker in PBMCs-derived macrophages might support a possible involvement of this cell subset in the pathogenesis of SSc.

References. 1.Wynn TA et al. Nat Med 2012;18:1028-40. 2.Fairweather D et al. J Autoimmun.2009 ;33 :222-30. 3.van den Hoogen F et al. Arthrit Rheum 2013;65:2737-47.

---

« Back to 2014 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/increased-number-of-cd206cells-in-peripheral-blood-and-skin-of-systemic-sclerosis-patients/