Changes in the lymph nodes during the earliest phases of rheumatoid arthritis

The RA-specific autoantibodies IgM rheumatoid factor (RF) and
anti-citrullinated protein antibodies (ACPA) can be present 10-14 years before
the development of RA. However, only a subset of the individuals who are
positive for RF and/or ACPA will develop RA over time. Currently, it is unknown
which subset of these autoantibody-positive individuals will make the
transition to the development of clinically apparent RA and which subset will
not, and why.

The fact that there are no clear signs of synovial inflammation (the synovium
is the main target tissue for inflammation in RA) in autoantibody-positive
individuals who subsequently develop RA suggests that synovial inflammation
develops in a (sub)acute way, which hampers studies of the target tissue during
the transition phase from being autoantibody-positive, and thereby at risk for
developing RA, to clinically apparent disease. This underscores the importance
of investigating other immune compartments than the synovium as well. As a
general principle, the recruitment of activated immune cells to the site of
inflammation is initiated after informing a nearby lymph node of a danger
signal. Thus, the immune reaction in lymph nodes generally precedes the influx
of effector cells into the target tissue. These results support our original
idea that we should additionally focus on the lymph nodes to get more insight
into the pathogenesis of the earliest phases of RA.
Using flow cytometry analysis we have already observed an increase in activated
CD8 positive CD69 positive T cells in early arthritis patients compared to
healthy controls. This may be in line with animal models of arthritis showing a
decreased CD4/CD8 ratio in lymph nodes before the onset of arthritis. However,
since none of the autoantibody-positive individuals in this cohort had as yet
developed arthritis, due to a short follow up period, future studies are needed
to confirm this. Second, we observed an increase in CD19 positive B cells in
early arthritis patients compared to healthy controls and a similar trend for
the autoantibody-positive individuals compared to healthy controls. The latter
would be in line with findings in animal models of arthritis.

In this project we will perform lymph node tissue analyses in 1)
autoantibody-positive individuals who are at risk of developing RA, 2) early
arthritis patients who do (RA) or do not (yet) (unclassified arthritis, UA)
fulfil 2010 ACR/EULAR classification criteria for RA, and 3)
autoantibody-negative healthy controls, in order to better understand
pathogenetic processes leading to the development of clinically manifest RA.

In this project builds on our earlier findings in about 80 persons and will
expand our knowledge.

We will pursue on the initial findings by:
1) further characterization of T-cell/B-cell/DC subsets and identification of
antigen-specificity in association with the development of RA, and their
antigen specificity.
2) evaluation of B- cell receptor (BCR) and T-cell receptor (TCR) repertoire.
3) identification of molecular processes involved in the earliest phases of RA
pathogenesis.

Observational cohort study with invasive procedure extending earlier findings

In total study participants will take part for 2 hours (healthy controls, early
RA/UA patients, autoantibody-positive individuals who do not develop RA) or 3
hours (autoantibody-positive individuals who do develop RA) in this study.
If applicable, study participants will have to stop anticoagulant therapy 3
days before until 1 day after the lymph node biopsy procedure. This will be
done in agreement with the patient and if necessary with the treating physician.
The lymph node biopsy procedure is generally well tolerated. Only a small
hematoma requiring no therapy occurs in most of the cases.