OBJECTIVE: Bruton's tyrosine kinase (BTK) transmits crucial survival signals from the B cell receptor (BCR) in B cells. Pharmacologic BTK inhibition effectively diminishes disease symptoms in mouse models of autoimmunity; conversely, transgenic BTK overexpression induces systemic autoimmunity in mice. We undertook this study to investigate BTK expression and activity in human B cells in the context of autoimmune disease. METHODS: Using intracellular flow cytometry, we quantified BTK expression and phosphorylation in subsets of peripheral blood B cells from 30 patients with rheumatoid arthritis (RA), 26 patients with primary Sjögren's syndrome (SS), and matched healthy controls. RESULTS: In circulating B cells, BTK protein expression levels correlated with BTK phosphorylation. BTK expression was up-regulated upon BCR stimulation in vitro and was significantly higher in CD27+ memory B cells than in CD27-IgD+ naive B cells. Importantly, BTK protein and phospho-BTK were significantly increased in B cells from anti-citrullinated protein antibody (ACPA)-positive RA patients but not in B cells from ACPA-negative RA patients. BTK was increased both in naive B cells and in memory B cells and correlated with frequencies of circulating CCR6+ Th17 cells. Likewise, BTK protein was increased in B cells from a major fraction of patients with primary SS and correlated with serum rheumatoid factor levels and parotid gland T cell infiltration. Interestingly, targeting T cell activation in patients with primary SS using the CTLA-4Ig fusion protein abatacept restored BTK protein expression in B cells to normal levels. CONCLUSION: These data indicate that autoimmune disease in humans is characterized by enhanced BTK activity, which is linked not only to autoantibody formation but also to T cell activity.
OBJECTIVE:Bruton's tyrosine kinase (BTK) transmits crucial survival signals from the B cell receptor (BCR) in B cells. Pharmacologic BTK inhibition effectively diminishes disease symptoms in mouse models of autoimmunity; conversely, transgenic BTK overexpression induces systemic autoimmunity in mice. We undertook this study to investigate BTK expression and activity in human B cells in the context of autoimmune disease. METHODS: Using intracellular flow cytometry, we quantified BTK expression and phosphorylation in subsets of peripheral blood B cells from 30 patients with rheumatoid arthritis (RA), 26 patients with primary Sjögren's syndrome (SS), and matched healthy controls. RESULTS: In circulating B cells, BTK protein expression levels correlated with BTK phosphorylation. BTK expression was up-regulated upon BCR stimulation in vitro and was significantly higher in CD27+ memory B cells than in CD27-IgD+ naive B cells. Importantly, BTK protein and phospho-BTK were significantly increased in B cells from anti-citrullinated protein antibody (ACPA)-positive RApatients but not in B cells from ACPA-negative RApatients. BTK was increased both in naive B cells and in memory B cells and correlated with frequencies of circulating CCR6+ Th17 cells. Likewise, BTK protein was increased in B cells from a major fraction of patients with primary SS and correlated with serum rheumatoid factor levels and parotid gland T cell infiltration. Interestingly, targeting T cell activation in patients with primary SS using the CTLA-4Ig fusion protein abatacept restored BTK protein expression in B cells to normal levels. CONCLUSION: These data indicate that autoimmune disease in humans is characterized by enhanced BTK activity, which is linked not only to autoantibody formation but also to T cell activity.
Authors: Stefan F H Neys; Peter Heukels; Jennifer A C van Hulst; Jasper Rip; Marlies S Wijsenbeek; Rudi W Hendriks; Odilia B J Corneth Journal: Cells Date: 2021-05-26 Impact factor: 6.600
Authors: Jasper Rip; Marjolein J W de Bruijn; Stefan F H Neys; Simar Pal Singh; Jonas Willar; Jennifer A C van Hulst; Rudi W Hendriks; Odilia B J Corneth Journal: Eur J Immunol Date: 2021-08-16 Impact factor: 6.688