Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Expression of Toll-Like Receptors 2, 4 and 9 by Peripheral Blood Leukocytes in Patients with ANCA-Associated Vasculitis.

Tadema3,  Henko, Abdulahad3,  Wayel H., Stegeman1,  Coen A., Kallenberg3,  Cees G. M., Heeringa2,  Peter

University Medical Center Groningen, Dept of Nephrology, Groningen, The Netherlands
University Medical Center Groningen, Dept of Pathology and Medical Biology, Groningen, The Netherlands
University Medical Center Groningen, Dept of Rheumatology and Clinical Immunology, Groningen, The Netherlands

Background:

Bacterial infections have been linked to the pathogenesis of ANCA-associated vasculitis (AAV), and nasal carriage of Staphylococcus aureus is associated with an increased risk for relapses. Toll-like receptors (TLRs) are important sensors of pathogen associated molecular patterns, and these receptors may be important during the development of relapses in AAV. Here, we characterized the expression of TLRs 2, 4, and 9 by peripheral blood leukocytes from AAV patients in remission. We compared TLR expression in patients who were nasal carriers of S. aureus and non-carriers. Furthermore, we studied the effect of in vitro ANCA-priming on TLR expression by monocytes.

Methods:

Expression of TLRs was determined using 9-color flowcytometry. Whole blood from 29 AAV patients (17 PR3-ANCA and 12 MPO-ANCA) and 19 matched healthy controls was stained for membrane markers CD3, CD14, CD16, CD19, CD27, and CD56 to distinguish between cell populations, and expression of membrane toll-like receptors (mTLR) 2, 4, and 9, and intracellular levels of TLR9 were determined. We compared TLR expression in AAV patients who were nasal carriers of S. aureus (n=9), and non-carriers (n=20). Peripheral blood mononuclear cells were stimulated in vitro with monoclonal anti-PR3 or PR3-ANCA IgG, and mTLR2 and mTLR4 expression by monocytes was determined.

Results:

Membrane expression of TLRs 2, 4, and 9 by B lymphocytes and T lymphocytes was comparable in AAV patients and controls. In AAV patients, we observed increased percentages of mTLR2+ (median=0.46% in AAV vs 0.18% in HC, p=0.01), and mTLR4+ (median 0.37% in AAV vs 0.22% in HC, p=0.02) NK cells. Monocytes from AAV patients expressed increased levels of mTLR2, compared to HC (median DMFI=31.7 in AAV vsD19.8 in HC, p=0.01). mTLR-expression by granulocytes was comparable in patients and controls. Intracellular levels of TLR9 (iTLR9) were decreased in B lymphocytes, T lymphocytes and NK cells from AAV patients, whereas monocytes and granulocytes expressed comparable iTLR9 levels. Within AAV patients, we observed increased mTLR4 expression by monocytes from nasal carriers of S. aureus, compared to non-carriers (mean DMFI=12.6 in Aureus+vs mean DMFI=5.8 in Aureus-, p=0.02). Priming with PR3-ANCA in vitro did not influence mTLR2 and mTLR4 expression by monocytes.

Conclusions:

We observed increased TLR expression by a proportion of NK cells and monocytes in AAV patients in remission, compared to healthy controls. It has been suggested that ANCA trigger monocytes to increase TLR expression, but we did not observe increased TLR expression after priming with PR3-ANCA in vitro. Interestingly, monocytes from nasal carriers of S. aureus expressed increased mTLR4 levels compared to non-carriers, indicating proinflammatory conditions. Increased TLR levels on NK cells and monocytes may reflect increased activation of these cells in AAV patients, but whether relapses can be triggered via TLRs will need further investigation.

To cite this abstract, please use the following information:
Tadema, Henko, Abdulahad, Wayel H., Stegeman, Coen A., Kallenberg, Cees G. M., Heeringa, Peter; Expression of Toll-Like Receptors 2, 4 and 9 by Peripheral Blood Leukocytes in Patients with ANCA-Associated Vasculitis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :2023
DOI: 10.1002/art.29788

Abstract Supplement

Meeting Menu

2010 ACR/ARHP