Bruton's tyrosine kinase separately regulates NFkappaB p65RelA activation and cytokine interleukin (IL)-10/IL-12 production in TLR9-stimulated B Cells.
B lymphocytes express both B cell receptor and Toll-like receptors (TLR). We show here that Bruton's tyrosine kinase (Btk), a critical component in B cell receptor signaling, is also involved in TLR9 signaling in B cells. Stimulation of B cells with TLR9 ligand CpG oligodeoxynucleotide (ODN) leads to transient phosphorylation of Btk, and in the absence of Btk, TLR9-induced proliferation of B cells is impaired. Interestingly, Btk(-/-) B cells secrete significantly more interleukin (IL)-12 but much less IL-10 compared with wild type B cells upon TLR9 stimulation. Immunization of Btk(-/-) mice with CpG ODN also leads to elevated levels of IL-12 in vivo and consequently, a greater -fold increment in the production of Th1 type IgG2b and IgG3 antibodies in these mice compared with wild type controls. The addition of exogenous recombinant IL-10 could suppress IL-12 production by TLR9-activated Btk(-/-) B cells, suggesting that in B cells, Btk negatively regulates IL-12 through the induction of autocrine IL-10 production. TLR9 signaling also leads to the activation of NFkappaB, including the p65RelA subunit in wild type B cells. The lack of Btk signaling affects the activation of NFkappaB and impairs the translocation of the p65RelA subunit to the nucleus of B cells upon TLR9 stimulation. However, p65RelA(-/-) B cells could respond similarly to wild type B cells in terms of IL-10 and IL-12 secretion when stimulated with CpG ODN, suggesting that the defect in NFkappaB p65RelA activation is additional to the impairment in cytokine production in TLR9-activated Btk(-/-) B cells. Thus, Btk plays an important role in TLR9 signaling and acts separately to regulate NFkappaB RelA activation as well as IL-10 and IL-12 production in B cells.
Lee
Koon-Guan
KG
Laboratory of Immunology, Bioprocessing Technology Institute, Agency for Science, Technology, and Research, Singapore, Singapore.
Xu
Shengli
S
Wong
Ee-Tsin
ET
Tergaonkar
Vinay
V
Lam
Kong-Peng
KP
D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology* / Q000378:metabolism; D018899:CpG Islands; D003600:Cytosol / Q000378:metabolism; D016753:Interleukin-10 / Q000378:metabolism*; D018664:Interleukin-12 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D008957:Models, Genetic; D009841:Oligonucleotides / Q000737:chemistry; D011505:Protein-Tyrosine Kinases / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D051217:Toll-Like Receptor 9 / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000378:metabolism*
D009841:Oligonucleotides; C495370:Tlr9 protein, mouse; D051217:Toll-Like Receptor 9; D051996:Transcription Factor RelA; D016753:Interleukin-10; D018664:Interleukin-12; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625951:Btk protein, mouse