Homozygous loss of ICOS is associated with adult-onset common variable immunodeficiency

Nat Immunol. 2003 Mar;4(3):261-8. doi: 10.1038/ni902. Epub 2003 Feb 10.


No genetic defect is known to cause common variable immunodeficiency (CVID), a heterogeneous human disorder leading to adult-onset panhypogammaglobulinemia. In a search for CVID candidate proteins, we found four of 32 patients to lack ICOS, the "inducible costimulator" on activated T cells, due to an inherited homozygous deletion in the ICOS gene. T cells from these individuals were normal with regard to subset distribution, activation, cytokine production and proliferation. In contrast, naive, switched and memory B cells were reduced. The phenotype of human ICOS deficiency, which differs in key aspects from that of the ICOS-/- mouse, suggests a critical involvement of ICOS in T cell help for late B cell differentiation, class-switching and memory B cell generation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, Differentiation, T-Lymphocyte / genetics*
  • B-Lymphocytes / physiology
  • CD28 Antigens / immunology
  • Cell Differentiation / immunology
  • Common Variable Immunodeficiency / genetics*
  • Homozygote*
  • Humans
  • Immunoglobulin A / blood
  • Immunoglobulin G / blood
  • Immunoglobulin M / blood
  • Immunologic Memory / immunology
  • Inducible T-Cell Co-Stimulator Protein
  • Receptors, Antigen, T-Cell / immunology
  • Sequence Deletion
  • T-Lymphocytes / physiology


  • Antigens, Differentiation, T-Lymphocyte
  • CD28 Antigens
  • ICOS protein, human
  • Icos protein, mouse
  • Immunoglobulin A
  • Immunoglobulin G
  • Immunoglobulin M
  • Inducible T-Cell Co-Stimulator Protein
  • Receptors, Antigen, T-Cell