The function of invariant chain in class ii-restricted antigen presentation

Stephanie Ceman, Andrea J. Sant

Research output: Contribution to journalArticlepeer-review


The role of invariant chain (Ii) in antigen presentation has been studied using two independent approaches. The first was to reconstitute cell lines with class II molecules and various forms of the Ii; the second has been to generate mice that lack functional expression of the Ii gene (Iio). Both types of studies show that Ii facilitates assembly of class II molecules in the endoplasmic reticulum (ER), chaperones or retains properly folded class II complexes through endosomal compartments, and finally, serves as a T-cell ligand. How Ii facilitates assembly of antigenic class II-peptide complexes is less clear and seems to depend on a number of factors reviewed here the antigen and epitope studied; the route and dose by which antigen is administered; the form of Ii present; and the responding T cell used in the experiment. During assembly of the class II-peptide complex, Ii may facilitate this process in a number of ways: specifically, by increasing the amount of class II available in endosomal vesicles; changing access or retention of class II molecules in the endosomal pathway; facilitating peptide exchange during CLIP dissociation, or finally, by modulating the antigen processing environment in the cell. In summary, we propose that instead of playing just one role in assembling the class II-peptide complex, Ii may perform all of the above described activities, functioning in different capacities along the pathway of antigen presentation.

Original languageEnglish (US)
Pages (from-to)373-387
Number of pages15
JournalSeminars in Immunology
Issue number6
StatePublished - 1995
Externally publishedYes


  • Antigen presentation
  • Class II
  • Invariant chain
  • Major histocompatibility complex

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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