Induction of dendritic cell maturation by pertussis toxin and its B subunit differentially initiate Toll-like receptor 4-dependent signal transduction pathways.
OBJECTIVE
Pertussis toxin (PT) has the capacity to activate dendritic cells (DCs) for the augmentation of cell-mediated immune responses. To investigate the mechanism(s) by which PT activates DCs, we investigated the effects of PT and its B-oligomer (PTB) on the maturation of human and mouse DCs and determined whether PT could act as a pathogen-associated molecular pattern to activate one of the Toll-like receptors (TLRs).


METHODS
The effects of PT and PTB on the maturation of human and mouse DCs were analyzed in terms of surface marker expression, cytokine production, antigen-presenting capacity, and intracellular signaling. The participation of TLR4 in PT-induced signaling was determined by comparing the effect of PT on DCs derived from TLR4-deficient and wild-type mice, as well as by measuring PT-induced NF-kappaB activation in HEK293 cells transiently transfected to express various TLRs.


RESULTS
Although both promoted phenotypic and functional maturation DCs, however, unlike PT that induced DC production of interleukin (IL)-6, tumor necrosis factor-alpha, IL-12, and interferon-inducible protein, PTB was capable of stimulating the production of interferon-inducible protein. Bone marrow-derived DCs from C3H/HeJ mice with defective TLR-4 alleles were unresponsive to PT and PTB, whereas DCs from C3H/HeN mice responded. In addition, PT induced NF-kappaB activation and IL-8 production in HEK293 cells transfected with a combination of TLR4 and MD2 but not in nontransfected or TLR2-transfected HEK293 cells. Comparison of the patterns of cytokine induction and intracellular signaling events in DCs treated by PT and PTB revealed that although PT, like lipopolysaccharide, triggered both MyD88-dependent and -independent pathways, PTB preferentially triggered MyD88-independent pathways. Interestingly, mouse splenocyte proliferation in response to PT and PTB was only partially dependent on TLR4.


CONCLUSIONS
The data identify PT as another pathogen-associated molecular pattern that induces DC maturation in a TLR4-dependent manner. Unlike PT, which triggers both MyD88-dependent and -independent pathways, PTB only triggers the MyD88-independent pathway in DCs.
Wang
Zhao Yuan
ZY
Intramural Basic Research Program, SAIC-Frederick, Inc, USA.
Yang
De
D
Chen
Qian
Q
Leifer
Cindy A
CA
Segal
David M
DM
Su
Shao Bo
SB
Caspi
Rachel R
RR
Howard
Zack O M
ZO
Oppenheim
Joost J
JJ
D000818:Animals; D003713:Dendritic Cells / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008809:Mice, Inbred C3H; D037342:Pertussis Toxin / Q000494:pharmacology*; D021122:Protein Subunits; D015398:Signal Transduction / Q000502:physiology*; D051197:Toll-Like Receptor 4 / Q000502:physiology*; D014162:Transfection
D021122:Protein Subunits; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D037342:Pertussis Toxin