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Infect. Immun., 08 1997, 3255-3260, Vol 65, No. 8
A Cauwels, E Wan, M Leismann and E Tuomanen
The cell wall is a key inflammatory agent of gram-positive bacteria.
Possible receptors mediating cell wall-induced inflammation include CD14
and platelet-activating factor (PAF) receptor. To delineate the conditions
under which these various receptors might be used, human monocytic THP-1
cells and heparinized whole human blood were stimulated with
lipopolysaccharide (LPS), intact Streptococcus pneumoniae bacteria, or
purified pneumococcal cell wall. THP-1 culture supernatant or cell-free
plasma was analyzed for the presence of tumor necrosis factor,
interleukin-1beta (IL-1beta), and IL-6. For the cultured monocytes,
anti-CD14 inhibited induction of the inflammatory cytokines by the cell
wall and LPS but not by intact pneumococcal bacteria. Despite the
difference in CD-14 usage, the intracellular pathways induced by the three
agents demonstrated similarities, as revealed in the presence of specific
signal transduction inhibitors such as cholera toxin, pertussis toxin, and
genistein. Cytokine production in whole human blood indicated that
anti-CD14 failed to block responses to cell wall and intact pneumococci,
whereas while LPS-induced responses were inhibited. PAF receptor antagonist
had no effect under any conditions in both assays. These results indicate
that although cell walls bind to both CD14 and PAF receptor, only CD14
appears to engender a cytokine response under restricted conditions.
Furthermore, host cell responses to intact pneumococci are consistently
independent of CD14 and PAF receptor.
Copyright © 1997, American Society for Microbiology
Coexistence of CD14-dependent and independent pathways for stimulation of human monocytes by gram-positive bacteria
Rockefeller University, New York, New York 10021, USA.
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