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Infect. Immun., Jun 1996, 1906-1912, Vol 64, No. 6
MG Cleveland, JD Gorham, TL Murphy, E Tuomanen and KM Murphy
Interleukin 12 (IL-12) strongly augments gamma interferon production by
natural killer (NK) and T cells. IL-12 also promotes effective cell-
mediated immune responses, which are particularly important against
intracellular bacteria such as Listeria monocytogenes. While the
lipopolysaccharide (LPS) of gram-negative bacteria induces monocyte
production of IL-12, the relevant gram-positive components which induce
IL-12 production are uncharacterized. We used the human monocytic cell line
THP-1 to study IL-12 induction by gram-positive bacteria. Muramyl
dipeptides as well as the major muramyl tetrapeptide component of
Streptococcus pneumoniae were inactive for inducing IL-12. In contrast,
lipoteichoic acid (LTA), a predominant surface glycolipid of gram- positive
bacteria, potently induced IL-12 p40 gene expression. A competitive LPS
antagonist, Rhodobacter sphaeroides LPS, inhibited LTA- induced IL-12
production, suggesting a common pathway for LPS and LTA in IL-12
activation. Pretreatment of cells with anti-CD14 monoclonal antibody
blocked both LPS and LTA induction of IL-12 p40 expression. LTA also
induced Thl development in naive CD4 T cells by an IL-12- dependent
mechanism, indicating direct induction of physiologic levels of IL-12.
Together, these results show that LTA is a potent surface structure of
gram-positive bacteria which induces IL-12 in monocytes through a
CD14-mediated pathway.
Copyright © 1996, American Society for Microbiology
Lipoteichoic acid preparations of gram-positive bacteria induce interleukin-12 through a CD14-dependent pathway
Division of Dermatology, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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