Background/Purpose: HLA B27 and gut bacteria are postulated to play a role in pathogenesis of Enthesitis Related Arthritis. Gut microbes can activate monocytes/macrophages by TLR pathway. However the mechanism of perpetuation of inflammation is not clear. Levels of endogenous ligands of TLR4 like myeloid Related Protein (MRP) 8/14 and Tenascin-C (TNC) are increased in patients with ERA. Thus we studied if monocytes from patients with ERA produce more pro-inflammatory cytokines in response to stimulation with TLR4 endogenous ligands (TNC and MRP8/14) as compared to healthy controls.

Methods: ERA patients satisfying ILAR criteria were enrolled. Whole blood was stimulated with TNC protein, MRP8/14 protein fragment, LPS or Proteoglycan for 24 hours and the culture supernatant was analyzed for IL-6 and TNF-alpha. Cytokine production was also measured by flow, cytometry after 6 hours culture and staining with antibodies against CD14, TNF-α and IL-6.

Results: 38 ERA patients (14.5 ± 3.6 years) with JSpADA score of (3.8 ± 1.15) and 23 healthy controls were enrolled. ERA patients showed significantly higher TNF-a production at baseline (18.4 ± 14.2 ng/ml for HC, 57.9 ± 53.21 ng/ml for ERA; p<0.05) as well as after stimulation by MRP8/14 (ERA-135.56 ± 165.51 ng/ml; p<0.05), Tenascin C (ERA-89.03 ± 81.8 ng/ml), LPS (ERA-583.38 ± 212.59 ng/ml) and PG ( ERA- 1104.43 ± 272.94 ng/ml) as compared to healthy subjects(p<0.05).

IL-6 production levels though not increased at baseline showed a significant increase after LPS (HC- 26.11 ± 7.62 pg/ml, ERA- 33.24 ± 6.49 pg/ml), PG (HC- 30.41 ± 10.63 pg/ml, ERA- 42.23 ± 6.35 pg/ml) and TNC (HC- 8.78 ± 7.39 pg/ml, ERA- 21.47 ± 9.43 pg/ml) stimulation (all p <0.01) as compared to healthy controls.

On flow cytometry also the ERA patients had higher frequency of TNF alpha producing monocytes as compared to healthy control (ERA-23.70 ± 12.0, p<0.01) at baseline. Stimulation with the endogenous ligands viz., MRP8 (HC-33.9 ± 6.9,ERA- 50.78 ± 15.74), TNC (HC- 22.4 ±10.2, ERA- 32.1 ± 15.16) and exogenous ligands viz., LPS (HC- 69.6 ±,12.2, ERA- 85.75 ± 14.64) and PG (HC-70.2 ± 12.1,ERA- 89.27 ± 11.15) led to a significant increase in the frequency of TNF-α producing monocyte frequency in ERA patients compared to healthy controls (p <0.01). Similar trend was seen in frequency of IL-6 producing cells.

Conclusion: : Patients with ERA have pre-activated monocytes in their peripheral blood. TLR4 endogenous ligands may be contributing to immune-inflammation by activating monocytes and leading to production of high levels of pro-inflammatory cytokines

« Back to 2017 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/monocytes-from-patients-with-enthesitis-related-arthritis-produce-high-levels-of-pro-inflammatory-cytokines-role-of-endogenous-ligands/