AB0011 KLRG1 as a marker of CD28 negativity in rheumatoid arthritis, comparison with CD57 and CD45RA
Authors: C Rawlings, E Choy, R Davies, G Jones, A Williams
Journal: Annals of the Rheumatic Diseases (2017)

<h3>Background</h3> Our research has shown that patients with RA have higher proportions of peripheral blood CD3+CD8+CD28- Treg cells compared to healthy individuals. CD3+CD8+CD28- Treg cells in patients with RA have lost their ability to suppress lymphocyte proliferation<sup>1</sup>. Thus CD28 negativity may mark senescent T cells. CD57<sup>2</sup> CD45RA<sup>3,4</sup> and killer-cell lectin like receptor G1 (KLRG1)<sup>5</sup> cell surface molecules have been associated with CD8+ T cell activation and senescence. Defining the phenotypic signature of CD8+CD28- Treg cells will help establish their significance in the immunoregulation of RA. <h3>Objectives</h3> To use immunofluorescence and flow cytometry to define the phenotype of CD3+CD8+CD28+/- cells in relation to early RA progression. <h3>Methods</h3> The effector characteristics of peripheral blood CD8 T cells were evaluated by flow cytometry. RA patients with established (n=21) and early disease (n=20) were recruited, and compared to twenty four healthy controls. The mean age of the subjects was 59 (SD=12.5), 25/38 (66%) were female, 27/38 (71%) were anti-CCP positive and 25/38 (66%) rheumatoid factor positive. The mean age for the controls was 43 (SD=11.6), 14/20 (70%) were female. <h3>Results</h3> Confirming our previous work, a significantly higher proportion of CD3+CD8+CD28- cells was observed in RA patients compared to healthy individuals (P=0.03) (Figure 1). Flow cytometric evaluation of peripheral blood demonstrated a significantly higher expression of CD57, CD45Ra and KLRG1 in CD28- compared to CD28+ T cells. A further evaluation of these markers revealed that 69% of the CD8+CD28- cell pool was KLRG1+, in comparison to 66% being CD57+ and 55% KLRG1+CD57+ double positive. This suggests that KLRG1 is a robust and clinically relevant marker of CD28- T cells in RA. Our current research is investigating the significance of KLRG1 and CD8+CD28- cells as prognostic markers in RA. <h3>Conclusions</h3> CD3+CD8+CD28- cells are enriched in the peripheral blood of RA patients. KLRG1 expression is increased in line with CD57 and CD45Ra in CD8+CD28- cells, and will be used to evaluate the functional significance of these cells in relation to their activation status and potential senescence in the immunoregulation of RA pathogenesis. <h3>References</h3> Ceeraz S, Hall C, Choy EH, Spencer J, Corrigall VM. Defective CD8+CD28+ regulatory T cell suppressor function in rheumatoid arthritis is restored by tumour necrosis factor inhibitor therapy. Clin Exp Immunol. 2013 Oct;174(1):18–26. Progressive decrease of CD8high+ CD28+ CD57- cells with ageing.Merino J, Martínez-González MA, Rubio M, Inogés S, Sánchez-Ibarrola A, Subirá ML Clin Exp Immunol. 1998 Apr; 112(1):48–51. CD28(-)CD8(+) T cells do not contain unique clonotypes and are therefore dispensable. Weinberger B, Welzl K, Herndler-Brandstetter D, Parson W, Grubeck-Loebenstein BImmunol Lett. 2009 Dec 2; 127(1):27–32. KLRG1 signaling induces defective Akt (ser473) phosphorylation and proliferative dysfunction of highly differentiated CD8+ T cells. Henson SM, Franzese O, Macaulay R, Libri V, Azevedo RI, Kiani-Alikhan S, Plunkett FJ, Masters JE, Jackson S, Griffiths SJ, Pircher HP, Soares MV, Akbar AN. Blood. 2009 Jun 25; 113(26):6619–28. <h3>Disclosure of Interest</h3> None declared