Chlamydia inhibits interferon γ-inducible major histocompatibility complex class II expression by degradation of upstream stimulatory factor 1

Guangming Zhong, Tao Fan, Li Liu

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164 Scopus citations


We report that chlamydiae, which are obligate intracellular bacterial pathogens, can inhibit interferon (IFN)-γ-inducible major histocompatibility complex (MHC) class II expression. However, the IFN-γ-induced IFN regulatory factor-1 (IRF-1) and intercellular adhesion molecule 1 (ICAM-1) expression is not affected, suggesting that chlamydia may selectively target the IFN-γ signaling pathways required for MHC class II expression. Chlamydial inhibition of MHC class II expression is correlated with degradation of upstream stimulatory factor (USF)-1, a constitutively and ubiquitously expressed transcription factor required for IFN-γ induction of class II transactivator (CIITA) but not of IRF-1 and ICAM-1. CIITA is an obligate mediator of IFN-γ-inducible MHC class II expression. Thus, diminished CIITA expression as a result of USF-1 degradation may account for the suppression of the IFN-γ-inducible MHC class II in chlamydia-infected cells. These results reveal a novel immune evasion strategy used by the intracellular bacterial pathogen chlamydia that improves our understanding of the molecular basis of pathogenesis.

Original languageEnglish (US)
Pages (from-to)1931-1937
Number of pages7
JournalJournal of Experimental Medicine
Issue number12
StatePublished - Jun 21 1999



  • Chlamydia upstream stimulatory factor 1
  • Interferon γ induction
  • Major histocompatibility complex class II
  • Protein degradation

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology

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