Background 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 proliferation1. Thus CD28 negativity may mark senescent T cells. CD572 CD45RA3,4 and killer-cell lectin like receptor G1 (KLRG1)5 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.
Objectives To use immunofluorescence and flow cytometry to define the phenotype of CD3+CD8+CD28+/- cells in relation to early RA progression.
Methods 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.
Results 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.
Conclusions 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.
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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.
Disclosure of Interest None declared