Integrin CD11b negatively regulates BCR signalling to maintain autoreactive B cell tolerance

Area of Science:

• Immunology
• Genetics
• Molecular Biology

Background:

• A specific variant of the integrin-α-M (CD11b) gene is associated with systemic lupus erythematosus (SLE) pathogenesis.
• The precise mechanisms by which this CD11b genotype contributes to the lupus phenotype remain unclear.

Purpose of the Study:

• To investigate the functional consequences of CD11b deficiency on autoreactive B cells.
• To elucidate the role of the lupus-associated CD11b variant (rs1143679) in B cell receptor (BCR) signaling.

Main Methods:

• Analysis of autoreactive B cells genetically deficient in CD11b.
• In vivo studies in CD11b-deficient mice.
• B cell transfection with wild-type or variant CD11b.
• Assessment of BCR signaling components, including tyrosine phosphorylation, calcium influx, and protein interactions.

Main Results:

• CD11b-deficient autoreactive B cells show hyperproliferation and enhanced survival upon BCR crosslinking.
• CD11b deficiency leads to increased autoantibody production and kidney immunoglobulin deposition in vivo.
• The lupus-associated CD11b variant abrogates CD11b's regulatory effect on BCR signaling by disrupting CD22 binding.
• Deficiency in CD11b results in altered tyrosine phosphorylation, reduced SHP-1 recruitment, and increased calcium influx.

Conclusions:

• CD11b plays a critical role in maintaining autoreactive B cell tolerance.
• The lupus-associated CD11b variant impairs this tolerance by disrupting CD11b-CD22 interactions and altering BCR signaling.
• Targeting CD11b or its signaling pathways may offer therapeutic strategies for systemic lupus erythematosus.