Skip to main content
. Author manuscript; available in PMC: 2014 Oct 2.
Published in final edited form as: Nat Rev Rheumatol. 2011 Jun 7;7(7):416–426. doi: 10.1038/nrrheum.2011.68

Figure 3.

Figure 3

A possible positive feedback cycle involving IL-1β and S100 proteins contributes to perpetuation of chronic inflammation in sJIA. Various pro-inflammatory stimuli, including IL-1β, lead to activation of monocytes and neutrophils. The activation of these cells is accompanied by increased secretion of S100 proteins, including S100-A8, S100-A9 and S100-A12. The proteins S100-A8 and S100-A9, which are markedly elevated in sJIA, form a complex called calprotectin that can serve as an endogenous agonist of TLR4 and trigger TLR signaling pathways, leading to activation of the transcription factor NFκB. Translocation of activated NFκB into the nucleus upregulates expression of IL-1β. In turn, increased IL-1β leads to further secretion of S100 proteins. In addition, S100-A8–S100-A9 complexes activate endothelial cells and also bind the integrin receptor CD11b/CD18 on phagocytes and stimulate their transendothelial migration into tissues.112,113 Abbreviations: IL, interleukin; M-CSF, macrophage colony-stimulating factor; NFκB, nuclear factor κB; TNF, tumor necrosis factor.