Dendritic cell function in allostimulation is modulated by C5aR signaling.
Regulation of T cell immunity by C5a has been suggested from recent studies. However, the underlying mechanisms, particularly the involved cells and biochemical basis, are not well defined. In this study, the direct modulation of dendritic cell (DC) activation and its function in T cell stimulation by C5a-C5aR interaction and the involved signaling pathways were investigated. We show that DCs from C5aR(-/-) mice and normal DCs treated with C5aR antagonist have less-activated phenotype characterized with increased IL-10 and decreased IL-12p70 production in response to LPS stimulation, lowered surface expression of MHC class II, B7.2, and consequently have reduced capacity to stimulate allospecific T cells. Conversely, C5a stimulation up-regulates DC activation and its function in allostimulation. Furthermore, stimulation of C5aR mediates the inhibition of cAMP production and protein kinase A activity and is involved in activation of PI3K/AKT and NF-kappaB signaling in DCs. These results demonstrate that C5a acts directly on C5aR expressed on DCs resulting in the cell activation and subsequently enhances its capacity for allospecific T cell stimulation. It also suggests that NF-kappaB signaling induced by down-regulation of cAMP/ protein kinase A pathway and up-regulation of PI3K/AKT pathway following C5a stimulation may contribute to up-regulation of DC function.
Complement Laboratory, MRC Centre for Transplantation, King's College London, School of Medicine at Guy's Hospital, London, UK.
Qi
Q
Peng
Ke
K
Li
Naiyin
N
Wang
Qijun
Q
Li
Elham
E
Asgari
Bao
B
Lu
Trent M
TM
Woodruff
Steven H
SH
Sacks
Wuding
W
Zhou
D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D015936:Complement C5a / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D000242:Cyclic AMP / Q000276:immunology / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000276:immunology / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology* / Q000378:metabolism; D016753:Interleukin-10 / Q000819:agonists / Q000276:immunology / Q000378:metabolism; D018664:Interleukin-12 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D007519:Isoantigens / Q000276:immunology* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000276:immunology / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000276:immunology / Q000378:metabolism; D044087:Receptor, Anaphylatoxin C5a / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology
D007519:Isoantigens; D008070:Lipopolysaccharides; D016328:NF-kappa B; D044087:Receptor, Anaphylatoxin C5a; D016753:Interleukin-10; D018664:Interleukin-12; D015936:Complement C5a; D000242:Cyclic AMP; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases