Patient material
SF was obtained from routine large joint aspiration from SLE, SpA and RA
patients fulfilling the 1982 ARA/ACR2,
ASAS11 and ACR classification criteria12 respectively. Informed consent was given prior to
SF and blood sampling, as approved by the local ethics committee.
Once collected, SF was centrifuged and stored as acellular at -80°C. In
parallel, paired serum samples were also processed. The mononuclear cell
fractions from SF (when present) and peripheral blood were collected
following gradient density centrifugation over Ficoll-Hypaque and were
cryopreserved in DMSO/FCS in N2(l) until use.
SLE synovial fluid samples, once retrieved, were selected for inclusion
in the present study after revision of the electronic clinical charts,
in order to exclude biological material from patients with evidence of
joint involvement not primarily dependent on SLE. We therefore revised
clinical information to exclude primary osteoarthritis, overlap with
rheumatoid arthritis, crystal related arthritis, and other comorbidities
which could entail potential confounders.
From an initial list of 27 patients, we therefore selected 17 SLE
patients with joint involvement, excluding 10 patients (1 with SLE RA
overlap, 1 with onset of arthritis after the occurrence of a
haematological malignancy, 8 for evidence of primary OA or crystal
related arthritis). The clinical characteristics are listed in Table 1
(SLE patients used for the cytokine analysis) and Supplementary Tables
S1 (RA patients used for the cytokine analysis) and S2 (patient samples
for cell analysis).