The role of lymphocyte crosstalk in autoimmune myositis

Supervisors: Professor Lucy Wedderburn and Dr Kiran Nistala

Hypothesis: this PhD will test the hypothesis that in children with juvenile dermatomyositis (JDM) there is dysregulation of B cells, particularly the immature B cell subset which rather than functioning in a regulatory manner, instead promotes inflammation, and so contributes to disease pathogenesis.

Background and Aims: The overall aim of this PhD will be to understand the contribution of B cells to the pathogenesis of JDM. JDM is a severe, potentially life threatening disease the cause of which is not at all understood (1,2). Evidence from model systems suggest that some B cell subsets may contribute to pathogenesis of autoimmune disease through IL-6 production or autoantibody production whilst others may play a regulatory role in an IL-10 dependent manner (3). Our pilot data suggest aberrations in B cell numbers and function in JDM. Identifying the exact nature of this dysregulation and the mechanisms that underpin it will be central to improving treatment for JDM. At present several powerful immune modulating treatments are used to treat autoimmune disease, yet we do not know exactly how these new drugs work. An example is B cell depletion with the anti CD20 antibody Rituximab, now being used for severe JDM with impressive responses in some patients but not in others (4). Understanding how effector and regulatory B cell balance, and the signalling pathways that govern their phenotype, alter disease expression in JDM will provide valuable insights for autoimmune disease in general and help us to use available therapies more effectively in the future.

Four central questions will be addressed in the PhD:

1. Are the frequency, absolute number and function of regulatory B cells (Breg) in JDM patients abnormal, and if so, does B cell regulatory and effector balance correlate with disease expression in childhood myositis?
2. Are IL-17 producing T cells raised in JDM and if so, do B cells from JDM patients promote the expansion of Th17 cells?
3. Is Blk signalling altered in T and B cells from patients with active JDM?
4. How do B cell abnormalities observed in JDM patients affect myositis in an in-vivo model system ?

Methods. This project will benefit from being linked to the UK National Cohort study of JDM which is based at ICH UCL, led by L Wedderburn, and has samples and linked data from over 410 children with JDM. The methods to be used in this project will be state-of-the-art cellular and molecular immunology. The Graduate student will learn 9 colour flow cytometry, cell sorting and cytokine secretion assays, sorting of subsets of cells as well as establishing functional assays for immune function, using both healthy control samples and those from children with juvenile myositis (5). They will then gain experience in cell signalling biology through the study of Blk signalling in B cells, and finally will have the opportunity to work on a murine model of myositis that we are establishing. Use of this model will provide the student with the opportunity to learn in vivo work, and to test mechanistically the role of both effector and regulatory B cell subsets in modulating myositis as well as Th17 effects. Together the project will provide an excellent and thorough training in both cellular and molecular immunology, as well as cell signalling and in vivo models of autoimmune disease. The student will benefit from working both in the Wedderburn lab at UCL Institute of Child Health, where there are strong links with the JDM clinic at Great Ormond Street Hospital, and also from the co supervision from Dr K Nistala (UCL), and collaboration with Prof C Mauri, UCL, for expertise on Breg and in vivo modelling work(6).

References:
1) Wedderburn, LR, & Rider, LG. Juvenile Dermatomyositis: New Developments in Pathogenesis, Assessment and Treatment. Best Practice & Res in Clin Rheumatol 25(3), 665-678 (2009).
2) Martin N, Krol P, et al. A national registry for juvenile dermatomyositis and other paediatric idiopathic inflammatory myopathies: 10 years experience; the Juvenile Dermatomyositis National Cohort Biomarker Study and Repository for Idiopathic Inflammatory Myopathies. Rheumatol 2011 Jan;50(1):137-45.
3) Barr TA, Shen P, et al. B cell depletion therapy ameliorates autoimmune disease through ablation of IL-6-producing B cells. J Exp Med 2012 May 7;209(5):1001-10
4) Cooper, MA et al. Rituximab for the treatment of juvenile dermatomyositis: a report of four pediatric patients. Arthritis Rheum 56, 3107-3111 (2007).
5) Nistala, K. Adams S, et al, Th17 plasticity in human autoimmune arthritis is driven by the inflammatory environment. Proc Natl Acad Sci USA 107 (33), 14751-14756
6) Blair, PA , Norena, L. et al., CD19(+)CD24(hi)CD38(hi) B cells exhibit regulatory capacity in healthy individuals but are functionally impaired in SLE patients. Immunity 32, 129-40 (2010)