Cellular composition of SLE synovial fluid
Subsequently, we were interested in the cellular composition found in SF
of SLE patients. SFMC were available from two SLE patients, one with as
multiple timepoints as described above and another with cells from two
timepoints. These samples were compared with SFMC from three SpA and two
age and sex matched seronegative RA patients. All samples were
investigated for T-cell phenotypes and when possible also for B cell,
monocyte and dendritic cell subsets (Supplementary Table S4).
In SLE SF, lymphocytes consisted mainly of CD3+ T cells, with CD8+ cells
being more common in SF than in PB (Fig. 2B, Supplementary Fig. 3A). B
cells which were rare (<1%) displayed a memory phenotype, for
one patient including age associated CD11c+ CD27+ B cells (Fig. 2B).
Examining the monocyte and dendritic cell (DC) subsets in SLE-SF,
64-67% of the HLA-DR+ cells expressed CD14 without expressing CD16, a
sign for classical monocytes (Fig.2B, Supplementary Fig. S3C).
Non-monocyte cells represented ~30% of HLA-DR+ cells in
SF, and were mostly classical DC (CD11c+, cDC), in patient one mainly
cDC1 while the other exhibited equal proportions of cDC1 and cDC2.The
frequency of plasmacytoid DC varied between patients from 7-26% (Fig.
2B, Supplementary Fig. S3C).