Background/Purpose: A paucity of known causative mechanisms in primary Sjögren’s Syndrome (pSS) contributes to inadequate classification criteria. However, known memory-phenotype B cell aberrations could enrich diagnostic criteria if such alterations precede clinical disease onset. Therefore, to determine diagnostic potential, we compared the phenotype and gene expression of B cells in pSS patients, sicca patients (individuals with symptoms but without pSS diagnosis), and healthy controls (HCs). 

Methods:

CD19^pos B cells from pSS (n=26), from sicca symptomatic patients (n=27), and from healthy controls (n=22) were analyzed using flow cytometry to identify canonical B cell subsets.  Sub-groups of these subjects were further analyzed for expression of CD21, CD23, CD24, CD95 CXCR5 and CD1c.  Additionally, purified B cell subsets (n=3-5, per group, per test) were analyzed for gene expression using Affymetrix gene arrays.

Results:

pSS patients had lower frequencies and numbers of CD27^pos/IgD^neg switched memory (SM) and CD27^pos/IgD^pos unswitched memory (UM) phenotype B cells compared with HCs. A sub-group of sicca patients shared a B cell profile similar to pSS.  Interestingly, lower UM B cell frequencies were evident in sicca patients before disease-associated autoantibodies were detectable. Importantly, patient UM B cell frequency significantly associated with serologic hyperactivity.  Extended phenotypic profiling in pSS revealed that the deficient UM cells had marginal zone B cell characteristics, whereas the SM cells were enriched for likely pathogenic effectors. CD27^pos memory B cell gene-expression profiling identified 135 differentially expressed genes between pSS patients and HCs.  Additionally, clustering analysis identified a subgroup of sicca patients with a gene expression profile similar to pSS. Whereas SM B cells gene expression analysis was similar in pSS and HCs, UM B cell gene expression analysis identified 187 differentially expressed genes between pSS patients and HCs. Interestingly, some of the these genes encoded signaling molecules and transcriptional factors associated with many B cell related biological pathways.

Conclusion:

Collectively, these findings suggest that UM B cells contribute to regulating autoimmunity and also that B cell profiling could enhance diagnosis of pSS onset.  Thus, B cell profiling in pSS has the potential to identify early disease-onset candidates for earlier therapeutic intervention and for novel therapies under investigation.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/memory-b-cell-phenotypic-and-gene-expression-profiling-in-primary-sjogrens-syndrome-implications-for-disease-diagnosis/