P053 Serum amyloid a can modulate neutrophil surface expression of l-selectin and integrin alpha m
Authors: T Kuret, K Lakota, P igon, M Ogric, S Sodin-Šemrl, R Ješe, S Cucnik, M Tomšic, A Hocevar
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Introduction</h3> Serum amyloid A (SAA) is one of the major acute phase proteins, elevated in the sera of newly diagnosed patients with giant cell arteritis (GCA).<sup>1</sup> SAA was previously shown to activate neutrophils and recently, neutrophils have been recognised as active players in GCA pathogenesis, exhibiting changes in surface protein expression of l-selectin (CD62L) and integrin αM (CD11b) during therapy tapering.<sup>2</sup> <h3>Objectives</h3> To determine the expression of CD62L and CD11b on neutrophils in peripheral blood of newly diagnosed, steroid naïve GCA patients (day 0) vs. healthy blood donors (HBDs). We also aimed to examine the ability of SAA and SAA1α to activate neutrophils in whole blood of HBDs and GCA patients prior to receiving glucocorticoid therapy and 7 and 30 days after therapy. <h3>Methods</h3> Whole blood of 37 GCA patients and 17 HBDs was stained with anti-CD62L and anti-CD11b (eBioscience), lysed and analysed by flow cytometer (Miltenyi). Whole blood of 5 GCA and 6 HBDs was stimulated with 10 µM hrSAA and hrSAA1α for 20 min at 37°C, lysed and incubated on melting ice for 15 min. Samples were then stained with anti-CD62L and anti-CD11b. SAA in sera of GCA patients was measured by nephelometry. <h3>Results</h3> We observed higher neutrophil counts and surface expression of CD62L in peripheral blood of naïve GCA patients compared to HBDs (p=0.006). Stimulation of whole blood with hrSAA or hrSAA1α significantly decreased CD62L and increased CD11b expression on neutrophils of HBDs and naïve GCA patients. Whole blood stimulation with hrSAA/SAA1α caused significant attenuation of CD62L, while increasing CD11b expression on neutrophils of naïve GCA patients (day 0) as compared to 7 and 30 days after therapy. Levels of SAA in GCA patients decreased after receiving therapy. <h3>Conclusions</h3> We show that hrSAA and hrSAA1α activate neutrophils implying tight adhesion and transendothelial migration. Interestingly however, in patients with GCA, increased SAA did not shed CD62L, as we observed elevation of both. The latter indicates potential initial attachment of neutrophils to activated endothelium, as a possible mechanism in GCA pathogenesis. <h3>References</h3> . 0'Neill L, <i>et al</i>. Regulation of inflammation and angiogenesis in giant cell arteritis by acute-phase serum amyloid A. Arthritis Rheum2015;67:2447–56. . Nadkarni S, et al. Investigational analysis reveals a potential role for neutrophils in GCA disease progression. Circ Res2014;114:242–48. <h3>Acknowledgements</h3> The authors would like to thank the Slovenian Research Agency (ARRS) for providing funding for the National Research program P3-0314, as well as the Rotary Club Zgornji Brnik, Slovenia for contributing funding for the flow cytometer. We would also like to thank Prof. Mauro Peretti and Dr. Suchita Nadkarni from WHRI, Queen Mary, University of London for their support in setting up the protocols. <h3>Disclosure of interest</h3> None declared