Targeting IL-6 by both passive or active immunization strategies prevents bleomycin-induced skin fibrosis

Arthritis Res Ther. 2014 Jul 24;16(4):R157. doi: 10.1186/ar4672.


Introduction: Interleukin-6 (IL-6) is a pleiotropic cytokine for which preliminary data have suggested that it might contribute to systemic sclerosis (SSc). Our aims were to investigate, firstly, IL-6 expression in patients with SSc and, secondly, the efficacy of both passive and active immunization against IL-6 to reduce skin fibrosis in complementary mouse models of SSc.

Methods: Human serum levels and skin expression of IL-6 were determined by enzyme-linked immunosorbent assay and immunohistochemistry, respectively. We first evaluated the antifibrotic properties of the monoclonal anti-IL-6R antibody, MR16-1, in the bleomycin-induced dermal fibrosis mouse model, reflecting early and inflammatory stages of SSc. Then, we assessed the efficacy of MR16-1 in tight skin-1 (Tsk-1) mice, an inflammation-independent model of skin fibrosis. Additionally, we have developed an innovative strategy using an anti-IL-6 peptide-based active immunization. Infiltrating leukocytes, T cells, and B cells were quantified, and IL-6 levels were measured in the serum and lesional skin of mice after passive or active immunization.

Results: Serum and skin levels of IL-6 were significantly increased in patients with early SSc. Treatment with MR16-1 led in the bleomycin mouse model to a 25% (P = 0.02) and 30% (P = 0.007) reduction of dermal thickness and hydroxyproline content, respectively. MR16-1 demonstrated no efficacy in Tsk-1 mice. Thereafter, mice were immunized against a small peptide derived from murine IL-6 and this strategy led in the bleomycin model to a 20% (P = 0.02) and 25% (P = 0.005) decrease of dermal thickness and hydroxyproline content, respectively. Passive and active immunization led to decreased T-cell infiltration in the lesional skin of mice challenged with bleomycin. Upon bleomycin injections, serum and skin IL-6 levels were increased after treatment with MR16-1 and were significantly reduced after anti-IL-6 active immunization.

Conclusions: Our results support the relevance of targeting IL-6 in patients with early SSc since IL-6 is overexpressed in early stages of the disease. Targeting IL-6 by both passive and active immunization strategies prevented the development of bleomycin-induced dermal fibrosis in mice. Our results highlight the therapeutic potential of active immunization against IL-6, which is a seductive alternative to passive immunization.

MeSH terms

  • Adult
  • Aged
  • Animals
  • Antibiotics, Antineoplastic / toxicity
  • Antibodies, Monoclonal / pharmacology*
  • Bleomycin / toxicity
  • Disease Models, Animal
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Fibrosis / chemically induced
  • Fibrosis / immunology
  • Fibrosis / prevention & control
  • Humans
  • Immunization / methods*
  • Immunohistochemistry
  • Interleukin-6 / antagonists & inhibitors*
  • Male
  • Mice
  • Middle Aged
  • Scleroderma, Systemic / immunology*
  • Skin Diseases / chemically induced
  • Skin Diseases / immunology
  • Skin Diseases / prevention & control*


  • Antibiotics, Antineoplastic
  • Antibodies, Monoclonal
  • Interleukin-6
  • Bleomycin