Background Patients with systemic autoimmune rheumatic diseases (SARD) often have a prolonged pre-clinical phase during which they are anti-nuclear antibody (ANA)+ but lack clinical symptoms. It has been proposed that progression from asymptomatic autoimmunity to clinical disease is accompanied by immunologic changes that could be used as predictors of disease development. Previous studies indicate that a number of B cell phenotypic changes are seen in SARD patients including changes in the proportions of various naïve and memory B cell subsets, increased B cell activation and elevated levels of plasmablasts/plasma cells.
Objectives To determine whether ANA+ individuals who lack sufficient symptoms for a SARD diagnosis have B cell phenotypic changes similar to those seen in SARD.
Methods Healthy controls (HC) and ANA+ individuals who: 1) lacked clinical symptoms of SARD (ANS); 2) had at least one clinical symptom of SARD (UCTD); or 3) had a recently diagnosed steroid and immunosuppressive naïve SARD (SLE, SS, SSc, MCTD, DM) were recruited. PBMCs were isolated over a Ficoll gradient, stained with various combinations of fluorescently labeled antibodies and analyzed by flow cytometry. Anti-nuclear antibodies were measured through the hospital laboratory. Whole blood IFN signature and BAFF RNA levels were measured by NanoString.
Results B cell phenotypes were examined for 32 HC, 38 ANS, 28 UCTD, and 59 early SARD (24 SS, 26 SSc, 6 SLE, 2 MCTD, 1 DM) patients. Patients with early SARD had a number of changes in their naïve and memory B cell subsets, as previously reported for patients with established disease, including: increased proportions of mature naïve B cells (SSc); increased proportions of T1T2 cells (SLE and SS); and trends to decreased proportions of switched memory B cells (CD27+IgD–) in all SARD. Similar decreases in the proportion of switched memory B cells were seen in ANS and UCTD patients, and as seen for the SARD patients, these cells were activated with elevated levels of CD86 as compared to HC. Significantly increased activation of the CD27–IgD– memory compartment was also seen in ANS, UCTD, SLE and SjD patients. Although significantly increased proportions of plasmablasts and/or CD138+ plasma cells were seen in all SARD patients (except those with SSc), these were not seen in ANS and UCTD patients. Nevertheless, in pre-SARD individuals (ANS + UCTD) there was a significant positive correlation between the size of these cell subsets, as well as the proportion of T1T2 cells, and ANA titer and the number of different anti-nuclear antibodies specificities. As observed for early SARD patients, there was a trend to increased BAFF levels as compared to HC in pre-SARD individuals, which achieved statistical significance in UCTD patients. However, there was no association between the levels of BAFF and any of the B cell phenotypes, whereas the IFN signature was positively associated with the proportion of T1T2 cells.
Conclusions B cell phenotypic abnormalities precede the onset of clinical disease in ANA+ individuals and have a pattern suggesting ongoing activation through T-B collaboration.
Disclosure of Interest None declared