Calreticulin in the immune system: ins and outs

Trends Immunol. 2013 Jan;34(1):13-21. doi: 10.1016/ Epub 2012 Sep 7.


Calreticulin is a calcium-binding chaperone that has several functions in the immune response. In the endoplasmic reticulum (ER), calreticulin facilitates the folding of major histocompatibility complex (MHC) class I molecules and their assembly factor tapasin, thereby influencing antigen presentation to cytotoxic T cells. Although calreticulin is normally ER-resident, it is found at the cell surface of living cancer cells and dying cells. Here, calreticulin promotes cellular phagocytic uptake. In tumor vaccine models, drugs that induce cell surface calreticulin confer enhanced tumor protection in an extracellular calreticulin-dependent manner. Much remains to be understood about the roles of calreticulin in these distinct functions. Further investigations are important towards advancing basic knowledge of glycoprotein-folding pathways, and towards developing new cancer therapeutic strategies.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Calreticulin / immunology*
  • Calreticulin / metabolism
  • Histocompatibility Antigens Class I / immunology
  • Humans
  • Immune System / chemistry
  • Immune System / immunology*
  • Intracellular Space / immunology
  • Phagocytes / immunology
  • Protein Folding


  • Calreticulin
  • Histocompatibility Antigens Class I