CD14 expression by human mononuclear phagocytes is modulated by Clostridium difficile toxin B.
Toxin B, an exotoxin produced by the anaerobic Gram-positive bacteria Clostridium difficile, is responsible for pseudomembranous colitis in humans. It deeply modifies morphology of cultured cells and enhances their membrane surface area, which suggests a possible alteration of membrane receptor distribution. Since toxin B and bacterial lipopolysaccharide can act synergistically on TNF-alpha production by mononuclear phagocytes, the effect of toxin B on CD14 expression was investigated using flow cytometric analysis. It was shown that monocytes overexpressed CD14 after 5 h of treatment with toxin B. In contrast, after 24 h of treatment, the percentage of CD14 monocytes decreased, although, most frequently, the remaining positive cells expressed high levels of CD14 compared with untreated cells. Macrophages treated for 5 h with toxin B overexpressed CD14, but this effect persisted for at least 24 h. Both the percentage of positive macrophages and the mean level of CD14 per cell were increased. Thus toxin B can modulate expression of CD14 and its modulation depends on the differentiation status and maybe on the activation state, since some individual variations were observed in monocyte response to toxin.
Siffert
J C
JC
LPCCNM-UPRES 2308, Illkirch, faculté de pharmacie, université Louis Pasteur, France.
Müller
C D
CD
Dumont
S
S
Monteil
H
H
Poindron
P
P
D001426:Bacterial Proteins; D001427:Bacterial Toxins / Q000494:pharmacology*; D002478:Cells, Cultured; D005434:Flow Cytometry; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000096:biosynthesis*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D018950:Lipopolysaccharide Receptors; C031815:toxB protein, Clostridium difficile