Autoimmune disease-associated haplotypes of BLK exhibit lowered thresholds for B cell activation and expansion of Ig class-switched B cells.
OBJECTIVE: B lymphoid kinase (BLK) is associated with rheumatoid arthritis (RA) and several other B cell-associated autoimmune disorders. BLK risk variants are consistently associated with reduced BLK expression, but the mechanisms by which reduced expression alters human B cell function to confer autoimmune disease susceptibility are unknown. This study was undertaken to characterize the BLK risk haplotype and to determine associated B cell functional phenotypes involved in autoimmunity. METHODS: The BLK risk haplotype association with RA (determined using whole-genome sequencing data) was confirmed in 2,526 RA cases and 2,134 controls. Peripheral blood mononuclear cells (PBMCs) from RA patients, healthy adults, and umbilical cord blood were used to study B cell functional phenotypes associated with the BLK risk genotype. Association of the BLK haplotype with B cell phenotypes was analyzed using cell culture and flow cytometry. RESULTS: Two insertion/deletions were found on the RA risk haplotype in BLK, and the reduction in BLK expression associated with the risk haplotype was confirmed in primary B lymphocytes. Carriers of the RA-associated haplotype had evidence of lower basal B cell receptor (BCR) signaling activity, yet their B cells were hyperactivatable, with enhanced up-regulation of CD86 after BCR crosslinking and greater T cell stimulatory capacity. The number of isotype-switched memory B cells was also significantly increased in subjects carrying the risk haplotype. CONCLUSION: A major mechanism underlying the BLK association with autoimmune disease involves lowered thresholds for BCR signaling, enhanced B cell-T cell interactions, and altered patterns of isotype switching.[1]References
- Autoimmune disease-associated haplotypes of BLK exhibit lowered thresholds for B cell activation and expansion of Ig class-switched B cells. Simpfendorfer, K.R., Armstead, B.E., Shih, A., Li, W., Curran, M., Manjarrez-Orduño, N., Lee, A.T., Diamond, B., Gregersen, P.K. Arthritis & Rheumatology (hoboken, N.j.) (2015) [Pubmed]
Annotations and hyperlinks in this abstract are from individual authors of WikiGenes or automatically generated by the WikiGenes Data Mining Engine. The abstract is from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.About WikiGenesOpen Access LicencePrivacy PolicyTerms of Useapsburg
