J Allergy Clin Immunol 2016[Mar]; 137 (3): 889-898.e6 PMID26478008show ga
Background: CD19 is a B-cell specific molecule that serves as a major co-stimulatory molecule for amplifying B cell receptor (BCR) responses. Bi-allelic CD19 gene mutations cause common variable immunodeficiency (CVID) in humans. BCR and TLR9 induced B-cell responses are impaired in most CVID patients. Objective: We sought to analyze whether CD19 is required for TLR9 function in human B cells. Methods: The expression of surface activation markers was assessed after anti-IgM or CpG stimulation using flow cytometry on B cells from patients with one or two defective CD19 alleles, which decrease or abrogate CD19 expression, respectively. The phosphorylation or interaction of signaling molecules was analyzed using phosphoflow cytometry, immunoblot or co-immunoprecipitation in CD19-deficient or control B cells and in a B cell line in which CD19 has been knocked-down using lentiviral transduced shRNA. Results: B cells from individuals with one or two defective CD19 alleles showed defective upregulation in vitro of CD86, TACI and CD23 activation markers after TLR9 stimulation. TLR9 ligands normally induce via MYD88/PYK2/LYN complexes the phosphorylation of CD19, which allows the recruitment of PI3K and the phosphorylation of BTK and AKT in human B cells with a different kinetic than that of BCRs. In addition, inhibition of PI3K, AKT or BTK as well as BTK-deficiency also result in TLR9 activation defects in B cells similar to those in CD19 deficiency. Conclusion: CD19 is required for TLR9-induced B-cell activation. Hence, CD19/PI3K/AKT/BTK is an essential axis integrating BCRs and TLR9 signaling in human B cells.
free
free
free
J+Allergy+Clin+Immunol 2016 ; 137 (3): 889-898.e6
