Central role of MyD88-dependent dendritic cell maturation and proinflammatory cytokine production to control Brucella abortus infection.
Brucella abortus is a facultative intracellular bacterium that infects humans and domestic animals. The enhanced susceptibility to virulent B. abortus observed in MyD88 knockout (KO) mice led us to investigate the mechanisms involved in MyD88-dependent immune responses. First, we defined the role of MyD88 in dendritic cell (DC) maturation. In vitro as well as in vivo, B. abortus-exposed MyD88 KO DCs displayed a significant impairment on maturation as observed by expression of CD40, CD86, and MHC class II on CD11c+ cells. In addition, IL-12 and TNF-alpha production was totally abrogated in MyD88 KO DCs and macrophages. Furthermore, B. abortus-induced IL-12 production was found to be dependent on TLR2 in DC, but independent on TLR2 and TLR4 in macrophages. Additionally, we investigated the role of exogenous IL-12 and TNF-alpha administration on MyD88 KO control of B. abortus infection. Importantly, IL-12, but not TNF-alpha, was able to partially rescue host susceptibility in MyD88 KO-infected animals. Furthermore, we demonstrated the role played by TLR9 during virulent B. abortus infection. TLR9 KO-infected mice showed 1 log Brucella CFU higher than wild-type mice. Macrophages and DC from TLR9 KO mice showed reduced IL-12 and unaltered TNF-alpha production when these cells were stimulated with Brucella. Together, these results suggest that susceptibility of MyD88 KO mice to B. abortus is due to impaired DC maturation and lack of IL-12 synthesis. Additionally, DC activation during Brucella infection plays an important regulatory role by stimulating and programming T cells to produce IFN-gamma.
Macedo
Gilson Costa
GC
Department of Biochemistry and Immunology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte-Minas Gerais, Brazil.
Magnani
Diogo Matos
DM
Carvalho
Natalia Barbosa
NB
Bruna-Romero
Oscar
O
Gazzinelli
Ricardo T
RT
Oliveira
Sergio Costa
SC
D000818:Animals; D002003:Brucella abortus; D002006:Brucellosis / Q000235:genetics / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism*; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology*; D007371:Interferon-gamma / Q000378:metabolism; D018664:Interleukin-12 / Q000494:pharmacology; D053762:Interleukin-12 Subunit p40 / Q000378:metabolism; D008198:Lymph Nodes / Q000276:immunology; D051379:Mice; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000502:physiology*; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D016207:Cytokines; D053762:Interleukin-12 Subunit p40; D053594:Myeloid Differentiation Factor 88; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9; D014409:Tumor Necrosis Factor-alpha; D018664:Interleukin-12; D007371:Interferon-gamma