IL-17A expression is localized to the inflamed joint.

<p>IL-17A protein levels were measured by MSD Assay in paired serum/synovial fluid samples (n = 20) (<b>A</b>). Synovial fluid levels were significantly higher than serum levels. Values expressed as median ± range, *p<0.01, significance level. Immunohistochemistry was performed in synovial tissue sections from patients with inflammatory arthritis (n = 19). (<b>B</b>).The number of mononuclear cells (white bars) staining for IL-17A was higher than the number of IL-17A positive polymorphonuclear cells (grey bars). Results are expressed as the number of IL-17A positive cells per high powered field (HPF). (<b>C</b>) Representative images of IL-17A expression in RA (i) vs. PsA (ii) and mononuclear IL-17A expression (iii) and polymorphonuclear IL-17A expression (iv).</p

Increased systemic expression of IL-17A at low pO2.

<p>(A) Patient synovial fluid samples (n = 22) were assessed by MSD assay for the expression of IL-17A. Cytokine levels were then grouped according to patient tpO₂ levels or >20mmHg. No significant difference in synovial fluid levels was observed between the two groups. (B) Synovial tissue pO₂ levels (n = 18) were also examined in relation to the expression of IL-17A positive mononuclear (white bars) and polymorphonuclear cells (grey bars). Patients with tpO₂ levels <20mmHg (n = 9) had significantly more IL-17A positive mononuclear cells than those with tpO₂ levels >20mmHg (n = 9) (p<0.05). Patients with tpO₂ levels <20mmHg (n = 9) also had a higher number of IL-17A positive polymorphonuclear cells than those with tpO₂ levels >20mmHg (n = 9). This difference was not statistically different. (C) Representative images of IL-17A expression on mononuclear cells from a patient with high tpO2 levels vs a patient with low tpO2 levels are shown.</p

Localisation of IL-17A to neutrophils and mast cells within the inflamed synovium.

<p>Representative images of RA synovial tissue section stained with antibodies against tryptase, CD15 and IL-17A. Merged images indicating co-localisation – yellow.</p

Results are expressed as mean (standard deviation) percentage.

<p>Results are expressed as mean (standard deviation) percentage.</p

The effect of 3% hypoxia on IL-17A and IL-6 <i>in vitro</i>.

<p>Peripheral blood mononuclear cells (n = 12) and neutrophils (n = 6) were cultured for 24hrs under 3% hypoxic conditions and normoxia. Hypoxia had no effect on IL-17A expression (A), but significantly induced IL-6 expression in mononuclear cells (B). Hypoxia had no effect on IL-17A(C) or IL-6 (D) in neutrophils. Data expressed as the mean <u>±</u> SEM. P<0.05 significantly different from normoxic conditions.</p