Open Access Highly Accessed Research article

Interleukin-7 deficiency in rheumatoid arthritis: consequences for therapy-induced lymphopenia

Frederique Ponchel12*, Robert J Verburg3, Sarah J Bingham2, Andrew K Brown2, John Moore4, Andrew Protheroe5, Kath Short5, Catherine A Lawson12, Ann W Morgan12, Mark Quinn2, Maya Buch2, Sarah L Field1, Sarah L Maltby1, Aurelie Masurel1, Susan H Douglas1, Liz Straszynski1, Ursula Fearon2, Douglas J Veale2, Poulam Patel5, Dennis McGonagle2, John Snowden6, Alexander F Markham1, David Ma4, Jacob M van Laar3, Helen A Papadaki7, Paul Emery2 and John D Isaacs128

Author Affiliations

1 Molecular Medicine Unit, University of Leeds, Leeds, UK

2 Academic Unit of Musculoskeletal Disease, Leeds General Infirmary, Leeds, UK

3 Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands

4 Hematology Department, St Vincent Hospital, Sydney, Australia

5 Cancer Research UK, University of Leeds, Leeds, UK

6 Department of Haematology, Royal Hallamshire Hospital, Sheffield, UK

7 Department of Hematology, University of Crete School of Medicine, Heraklion, Crete, Greece

8 School of Clinical Medical Sciences (Musculoskeletal Research Group), The University of Newcastle, Newcastle upon Tyne, UK

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Arthritis Res Ther 2005, 7:R80-R92  doi:10.1186/ar1452

Published: 16 November 2004

Abstract

We previously demonstrated prolonged, profound CD4+ T-lymphopenia in rheumatoid arthritis (RA) patients following lymphocyte-depleting therapy. Poor reconstitution could result either from reduced de novo T-cell production through the thymus or from poor peripheral expansion of residual T-cells. Interleukin-7 (IL-7) is known to stimulate the thymus to produce new T-cells and to allow circulating mature T-cells to expand, thereby playing a critical role in T-cell homeostasis. In the present study we demonstrated reduced levels of circulating IL-7 in a cross-section of RA patients. IL-7 production by bone marrow stromal cell cultures was also compromised in RA. To investigate whether such an IL-7 deficiency could account for the prolonged lymphopenia observed in RA following therapeutic lymphodepletion, we compared RA patients and patients with solid cancers treated with high-dose chemotherapy and autologous progenitor cell rescue. Chemotherapy rendered all patients similarly lymphopenic, but this was sustained in RA patients at 12 months, as compared with the reconstitution that occurred in cancer patients by 3–4 months. Both cohorts produced naïve T-cells containing T-cell receptor excision circles. The main distinguishing feature between the groups was a failure to expand peripheral T-cells in RA, particularly memory cells during the first 3 months after treatment. Most importantly, there was no increase in serum IL-7 levels in RA, as compared with a fourfold rise in non-RA control individuals at the time of lymphopenia. Our data therefore suggest that RA patients are relatively IL-7 deficient and that this deficiency is likely to be an important contributing factor to poor early T-cell reconstitution in RA following therapeutic lymphodepletion. Furthermore, in RA patients with stable, well controlled disease, IL-7 levels were positively correlated with the T-cell receptor excision circle content of CD4+ T-cells, demonstrating a direct effect of IL-7 on thymic activity in this cohort.

Keywords:
immune reconstitution; interleukin-7; T-cell differentiation; therapeutic lymphodepletion