MyD88 primes macrophages for full-scale activation by interferon-gamma yet mediates few responses to Mycobacterium tuberculosis.

TitleMyD88 primes macrophages for full-scale activation by interferon-gamma yet mediates few responses to Mycobacterium tuberculosis.
Publication TypeJournal Article
Year of Publication2003
AuthorsShi S, Nathan C, Schnappinger D, Drenkow J, Fuortes M, Block E, Ding A, Gingeras TR, Schoolnik G, Akira S, Takeda K, Ehrt S
JournalJ Exp Med
Date Published2003 Oct 06
KeywordsAdaptor Proteins, Signal Transducing, Animals, Antigens, Differentiation, Gene Expression Regulation, Interferon-gamma, Interleukin-1, Macrophage Activation, Macrophages, Membrane Glycoproteins, Mice, Mice, Inbred C57BL, Mycobacterium tuberculosis, Myeloid Differentiation Factor 88, NF-kappa B, Receptors, Cell Surface, Receptors, Immunologic, Toll-Like Receptors, Transcriptional Activation, Tumor Necrosis Factor-alpha

Macrophages are activated from a resting state by a combination of cytokines and microbial products. Microbes are often sensed through Toll-like receptors signaling through MyD88. We used large-scale microarrays in multiple replicate experiments followed by stringent statistical analysis to compare gene expression in wild-type (WT) and MyD88-/- macrophages. We confirmed key results by quantitative reverse transcription polymerase chain reaction, Western blot, and enzyme-linked immunosorbent assay. Surprisingly, many genes, such as inducible nitric oxide synthase, IRG-1, IP-10, MIG, RANTES, and interleukin 6 were induced by interferon (IFN)-gamma from 5- to 100-fold less extensively in MyD88-/- macrophages than in WT macrophages. Thus, widespread, full-scale activation of macrophages by IFN-gamma requires MyD88. Analysis of the mechanism revealed that MyD88 mediates a process of self-priming by which resting macrophages produce a low level of tumor necrosis factor. This and other factors lead to basal activation of nuclear factor kappaB, which synergizes with IFN-gamma for gene induction. In contrast, infection by live, virulent Mycobacterium tuberculosis (Mtb) activated macrophages largely through MyD88-independent pathways, and macrophages did not need MyD88 to kill Mtb in vitro. Thus, MyD88 plays a dynamic role in resting macrophages that supports IFN-gamma-dependent activation, whereas macrophages can respond to a complex microbial stimulus, the tubercle bacillus, chiefly by other routes.

Alternate JournalJ Exp Med
PubMed ID14517275
PubMed Central IDPMC2194223
Grant ListHL 68525 / HL / NHLBI NIH HHS / United States
AI 30165 / AI / NIAID NIH HHS / United States
R01 AI030165 / AI / NIAID NIH HHS / United States
R01 HL068525 / HL / NHLBI NIH HHS / United States
HL 61241 / HL / NHLBI NIH HHS / United States

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