Dinucleotide repeat expansion in the CTLA-4 gene leads to T cell hyper-reactivity via the CD28 pathway in myasthenia gravis

J Neuroimmunol. 2000 Jun 1;105(1):69-77. doi: 10.1016/s0165-5728(00)00191-0.


CD28 is required to promote T cell proliferation and cytokine production, while the cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) functions as a negative modulator for T cell activation. We previously reported that alleles with longer PCR products (designated as allele xx) in an (AT)n polymorphism in Ctla-4 are associated with myasthenia gravis with thymoma, while the shortest allele, 86, is negatively associated with the disease. Here, we demonstrate that serum IL-2 sRalpha increases parallel to the length of (AT)n in Ctla-4. Periphereal blood mononuclear cells (PBMC) from patients with Ctla-4 xx/xx contained higher activity of telomerase than patients bearing Ctla-4 86/86. Blockade of CTLA-4 increased the telomerase activity in PBMC stimulated by acetylcholine receptor in vitro. There was a positive correlation between the expression of CD28 and CTLA-4 on anti-CD3 activated PBMC, suggesting a balance between CD28 and CTLA-4. Cells from patients with Ctla-4 xx/xx had the highest level of T cell proliferative responses upon the addition of anti-CD28 antibodies to the anti-CD3 containing culture system while cells from patients with Ctla-4 86/xx had an intermediate and cells from patients with Ctla-4 86/86 the lowest increase. The current results point to the (AT)n in Ctla-4 as a myasthenia gravis facilitating mutation under certain permissive environments by influencing the T cell reactivity via the CD28 pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abatacept
  • Antigens, CD
  • Antigens, Differentiation / genetics*
  • CD28 Antigens / physiology*
  • CD3 Complex / immunology
  • CTLA-4 Antigen
  • Cells, Cultured
  • Dinucleotide Repeats*
  • Humans
  • Immunoconjugates*
  • Lymphocyte Activation*
  • Myasthenia Gravis / immunology*
  • Receptors, Interleukin-2 / analysis
  • T-Lymphocytes / immunology*
  • Telomerase / metabolism


  • Antigens, CD
  • Antigens, Differentiation
  • CD28 Antigens
  • CD3 Complex
  • CTLA-4 Antigen
  • CTLA4 protein, human
  • Immunoconjugates
  • Receptors, Interleukin-2
  • Abatacept
  • Telomerase