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Infection and Immunity, October 2000, p. 5525-5529, Vol. 68, No. 10
Department of Microbiology and Immunology,
Wake Forest University School of Medicine, Winston-Salem, North
Carolina 27157
Received 25 May 2000/Accepted 28 June 2000
Flagella from diverse gram-negative bacteria induce tumor necrosis
factor alpha (TNF-
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
High-Affinity Interaction between Gram-Negative
Flagellin and a Cell Surface Polypeptide Results in Human
Monocyte Activation
) and interleukin-1
(IL-1
) synthesis by
human monocytes (F. Ciacci-Woolwine, P. F. McDermott, and S. B. Mizel, Infect. Immun. 67:5176-5185, 1999). In this study, we establish that purified flagellin (FliC or FljB), the major filament protein from Salmonella enterica serovar Enteritidis,
S. enterica serovar Typhimurium, and Pseudomonas
aeruginosa, is an extremely potent inducer of TNF-
production
by human monocytes and THP-1 myelomonocytic cells. Fifty percent of
maximal TNF-
production (EC50) was obtained with
1.5 × 10
11 M flagellin (0.75 ng/ml). Mutagenesis
studies revealed that the central hypervariable region of flagellin is
essential for the TNF-
-inducing activity of the protein. Although
less active than the wild-type protein, a Salmonella
flagellin mutant composed of only the central hypervariable region
retained substantial TNF-
-inducing activity at nanomolar
concentrations. In contrast, the conserved amino- and carboxy-terminal
regions are inactive. Mutational analysis of the hypervariable region
revealed that it contains two equally active TNF-
-inducing domains.
The ability of THP-1 cells to respond to purified flagellins is
dramatically reduced by mild trypsin treatment of the cells. Taken
together, our results demonstrate that the cytokine-inducing activity
of flagellins from gram-negative bacteria results from the interaction of these proteins with high-affinity cell surface polypeptide receptors
on monocytes.
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157. Phone: (336) 716-2216. Fax: (336) 716-9928. E-mail: smizel{at}wfubmc.edu.
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