| Autor: |
Dellacasagrande, Jérôme, Ghigo, Eric, Machergui-El, Sarah, Hammami, Toman, Rudolf, Raoult, Didier, Capo, Christian, Mege, Jean-Louis |
| Zdroj: |
Infection and Immunity; October 2000, Vol. 68 Issue: 10 p5673-5678, 6p |
| Abstrakt: |
ABSTRACTCoxiella burnetii, the agent of Q fever, enters human monocytes through αvβ3integrin and survives inside host cells. In addition, C. burnetiistimulates the synthesis of inflammatory cytokines including tumor necrosis factor (TNF) by monocytes. We studied the role of the interaction of C. burnetiiwith THP-1 monocytes in TNF production. TNF transcripts and TNF release reached maximum values within 4 h. Almost all monocytes bound C. burnetiiafter 4 h, while the percentage of phagocytosing monocytes did not exceed 20%. Cytochalasin D, which prevented the uptake of C. burnetiiwithout interfering with its binding, did not affect the expression of TNF mRNA. Thus, bacterial adherence, but not phagocytosis, is necessary for TNF production by monocytes. The monocyte αvβ3integrin was involved in TNF synthesis since peptides containing RGD sequences and blocking antibodies against αvβ3integrin inhibited TNF transcripts induced by C. burnetii. Nevertheless, the cross-linking of αvβ3integrin by specific antibodies was not sufficient to induce TNF synthesis. The signal delivered by C. burnetiiwas triggered by bacterial lipopolysaccharide (LPS). Polymyxin B inhibited the TNF production stimulated by C. burnetii, and soluble LPS isolated fromC. burnetiilargely mimicked viable bacteria. On the other hand, avirulent variants of C. burnetiiinduced TNF production through an increased binding to monocytes rather than through the potency of their LPS. We suggest that the adherence ofC. burnetiito monocytes via αvβ3integrin enables surface LPS to stimulate TNF production in THP-1 monocytes. |
| Databáze: |
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