18A130

Comparison of B and T cell subsets, cytokine expression and synovial pathology in Down’s Arthritis (DA) and Juvenile Idiopathic Arthritis (JIA)

Author(s)

Charlene Foley1, Achilleas Floudas2, Mary Canavan2, Monika Biniecka2, Emma-Jane MacDermott1, Orla G Killeen1, Ronan Mullan3 and Ursula Fearon2

Department(s)/Institutions

1 National Centre for Paediatric Rheumatology 2 Trinity Biomedical Sciences Institute 3 Tallaght Hospital

Introduction

A pathological feature of Down syndrome (DS) is dysregulation of the immune system. This almost certainly contributes to the high incidence of autoimmune diseases observed in this cohort. Previous work by our group suggests that the prevalence of Down's Arthritis (DA) is 18-21 fold greater than JIA. Children with DA often follow an erosive, polyarticular course of disease with small joint involvement observed in a significantly greater proportion (p<0.01) of children than expected in a typical JIA cohort. The DA clinical phenotype may be distinct from JIA, however little is known about the differences in synovial pathology or immunological regulation. Indeed no studies to date have examined these entities in DA.

Aims/Background

To examine B-cell subsets and T cell cytokine profiles; and characterise and compare the synovial membrane immunohistochemistry in children with DA and JIA.

Method

Multicolour flow-cytometry was used to analyse the phenotype of B-cells and T-cell cytokines in PBMCs from 40 children, n=10 per group; Healthy Control (HC), JIA, DS, DA. Cells were stained with the following panels;
B-cells (CD38, CD24, CD20, CD80, CD27, IgM, CD138, CD45, CD19, MHCclassII, BCMA, CD40, CD86, IgD);
T-cell cytokines analysed after 5hours PMA/Ionomycin stimulation (CD3, CD8, CD161, IFN-γ, TNF-α, IL-17a, GM-CSF).
Flow cytometry data was assessed by Flowjo software.

Synovial tissue was obtained through US-guided biopsy and analysed by immunohistochemistry for CD3, CD20, CD68, FVIII (DA n=3; JIA n=4).

Results

Flow cytometry analysis revealed that children with DA have a significantly lower number of circulating CD19+CD20+ B-cells when compared to children with JIA (p<0.05) and HC (p<0.001); however a greater proportion of memory B-cells (CD27+) when compared to children with DS (p<0.05).

IFN-γ and TNF-α production by CD8+/CD8- T-cells was greater in DA compared to both JIA (CD8+IFNγ+ p<0.001; CD8+TNFα+ p<0.01; CD8-IFNγ + p<0.05; CD8-TNFα p<0.05) and HC (CD8+IFNγ+ p<0.05; CD8+TNFα+ p<0.05; CD8-IFNγ+ p<0.05; CD8-TNFα p<0.01).

Examination of synovial tissue from children with DA demonstrated higher levels of CD3+cells, Macrophages (p<0.05), CD20+cells and FVIII.

Conclusions

There are significant differences in B-cell populations, T-cell cytokine production and immunohistochemical features of synovial tissue in children with DA and JIA. More work is required to verify these results.