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Cytotoxic T-lymphocyte-associated protein 4
CTLA4 Crystal Structure.rsh.png
Structure of murine CTLA4 (CD152)
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols CTLA4 ; CD; CD152; CELIAC3; CTLA-4; GRD4; GSE; IDDM12
External IDs OMIM123890 MGI88556 HomoloGene3820 GeneCards: CTLA4 Gene
RNA expression pattern
PBB GE CTLA4 221331 x at tn.png
More reference expression data
Species Human Mouse
Entrez 1493 12477
Ensembl ENSG00000163599 ENSMUSG00000026011
UniProt P16410 P09793
RefSeq (mRNA) NM_001037631 NM_001281976
RefSeq (protein) NP_001032720 NP_001268905
Location (UCSC) Chr 2:
204.73 – 204.74 Mb
Chr 1:
60.89 – 60.92 Mb
PubMed search [1] [2]

CTLA4 or CTLA-4 (cytotoxic T-lymphocyte-associated protein 4), also known as CD152 (cluster of differentiation 152), is a protein receptor that downregulates the immune system. CTLA4 is found on the surface of T cells, which lead the cellular immune attack on antigens. The T cell attack can be turned on by stimulating the CD28 receptor on the T cell. The T cell attack can be turned off by stimulating the CTLA4 receptor, which acts as an "off" switch.

The CTLA-4 protein is encoded by the ctla4 gene in mouse[1] and the CTLA4 gene in human.[2]

Function and mechanism[edit]

CTLA4 is a member of the immunoglobulin superfamily, which is expressed on the surface of Helper T cells and transmits an inhibitory signal to T cells. CTLA4 is similar to the T-cell co-stimulatory protein, CD28, and both molecules bind to CD80 and CD86, also called B7-1 and B7-2 respectively, on antigen-presenting cells. CTLA4 transmits an inhibitory signal to T cells,[3][4][5][6] whereas CD28 transmits a stimulatory signal.[7][8] Intracellular CTLA4 is also found in regulatory T cells and may be important to their function. T cell activation through the T cell receptor and CD28 leads to increased expression of CTLA-4, an inhibitory receptor for B7 molecules.

The mechanism by which CTLA-4 acts in T cells remains somewhat controversial. Biochemical evidence suggested that CTLA-4 recruited a phosphatase to the T cell receptor, thus attenuating the signal.[9] This work remains unconfirmed in the literature since its first publication. More recent work has suggested that CTLA-4 may function in vivo by capturing and removing B7-1 and B7-2 from the membranes of antigen-presenting cells, thus making these unavailable for triggering of CD28.[10]

CTLA-4 may also function via modulation of cell motility and/or signaling through PI3 kinase[11] Early multiphoton microscopy studies observing T-cell motility in intact lymph nodes appeared to give evidence for the so-called ‘reverse-stop signaling model’.[12] In this model CTLA 4 reverses the TCR-induced ‘stop signal’ needed for firm contact between T cells and antigen-presenting cells (APCs).[13] However, those studies compared CTLA-4 positive cells, which are predominantly regulatory cells and are at least partially activated, with CTLA-4 negative naive T cells. The disparity of these cells in multiple regards may explain some of these results. Other groups who have analyzed the effect of antibodies to CTLA-4 in vivo have concluded little or no effect upon motility.[14] Antibodies to CTLA-4 may exert additional effects when used in vivo, by binding and thereby depleting regulatory T cells.[15]


The protein contains an extracellular V domain, a transmembrane domain, and a cytoplasmic tail. Alternate splice variants, encoding different isoforms, have been characterized. The membrane-bound isoform functions as a homodimer interconnected by a disulfide bond, while the soluble isoform functions as a monomer. The intracellular domain is similar to that of CD28, in that it has no intrinsic catalytic activity and contains one YVKM motif able to bind PI3K, PP2A and SHP-2 and one proline-rich motif able to bind SH3 containing proteins. The first role of CTLA-4 in inhibiting T cell responses seem to be directly via SHP-2 and PP2A dephosphorylation of TCR-proximal signalling proteins such as CD3 and LAT. CTLA-4 can also affect signalling indirectly via competing with CD28 for CD80/86 binding. CTLA-4 can also bind PI3K, although the importance and results of this interaction are uncertain.

Clinical significance[edit]

Mutations in this gene have been associated with insulin-dependent diabetes mellitus, Graves' disease, Hashimoto's thyroiditis, celiac disease, systemic lupus erythematosus, thyroid-associated orbitopathy, primary biliary cirrhosis and other autoimmune diseases.

Polymorphisms of the CTLA-4 gene are associated with autoimmune diseases such as autoimmune thyroid disease and multiple sclerosis, though this association is often weak. In Systemic Lupus Erythematosus (SLE), the splice variant sCTLA-4 is found to be aberrantly produced and found in the serum of patients with active SLE.

Agonists to reduce immune activity[edit]

The comparatively higher binding affinity of CTLA4 has made it a potential therapy for autoimmune diseases. It plays a role in the initial immune response to and infection of immune cells by, HIV, along with the PD-1 pathway and others. Fusion proteins of CTLA4 and antibodies (CTLA4-Ig) have been used in clinical trials for rheumatoid arthritis.[16] The fusion protein CTLA4-Ig is commercially available as Orencia (abatacept). A second generation form of CTLA4-Ig known as belatacept was recently approved by the FDA based on favorable results from the randomized Phase III BENEFIT (Belatacept Evaluation of Nephroprotection and Efficacy as First Line Immunosuppression) study. It was approved for renal transplantation in patients that are sensitized to EBV, or Epstein Barr Virus.

Antagonists to increase immune activity[edit]

Conversely, there is increasing interest in the possible therapeutic benefits of blocking CTLA4 (using antagonistic antibodies against CTLA such as ipilimumab (FDA approved for melanoma in 2011) as a means of inhibiting immune system tolerance to tumours and thereby providing a potentially useful immunotherapy strategy for patients with cancer. This is the first approved immune checkpoint blockade therapy.[17]


CTLA-4 has been shown to interact with:


  1. ^ Brunet JF, Denizot F, Luciani MF, Roux-Dosseto M, Suzan M, Mattei MG, Golstein P (1987). "A new member of the immunoglobulin superfamily--CTLA-4". Nature 328 (6127): 267–70. doi:10.1038/328267a0. PMID 3496540. 
  2. ^ Dariavach P, Mattéi MG, Golstein P, Lefranc MP (December 1988). "Human Ig superfamily CTLA-4 gene: chromosomal localization and identity of protein sequence between murine and human CTLA-4 cytoplasmic domains". Eur. J. Immunol. 18 (12): 1901–5. doi:10.1002/eji.1830181206. PMID 3220103. 
  3. ^ Krummel MF, Allison JP (1995). "CD28 and CTLA-4 have opposing effects on the response of T cells to stimulation". J. Exp. Med. 182 (2): 459–65. PMC 2192127. PMID 7543139. 
  4. ^ Walunas TL, Bakker CY, Bluestone JA (1996). "CTLA-4 ligation blocks CD28-dependent T cell activation". J. Exp. Med. 183 (6): 2541–50. PMC 2192609. PMID 8676075. 
  5. ^ Walunas TL, Lenschow DJ, Bakker CY, Linsley PS, Freeman GJ, Green JM, Thompson CB, Bluestone JA (August 1994). "CTLA-4 can function as a negative regulator of T cell activation". Immunity 1 (5): 405–13. PMID 7882171. 
  6. ^ Waterhouse P, Penninger JM, Timms E, Wakeham A, Shahinian A, Lee KP, Thompson CB, Griesser H, Mak TW (November 1995). "Lymphoproliferative disorders with early lethality in mice deficient in Ctla-4". Science 270 (5238): 985–8. doi:10.1126/science.270.5238.985. PMID 7481803. 
  7. ^ Harding FA, McArthur JG, Gross JA, Raulet DH, Allison JP (1992). "CD28-mediated signalling co-stimulates murine T cells and prevents induction of anergy in T-cell clones". Nature 356 (6370): 607–9. doi:10.1038/356607a0. PMID 1313950. 
  8. ^ Magistrelli G, Jeannin P, Herbault N, Benoit De Coignac A, Gauchat JF, Bonnefoy JY, Delneste Y (November 1999). "A soluble form of CTLA-4 generated by alternative splicing is expressed by nonstimulated human T cells". Eur. J. Immunol. 29 (11): 3596–602. doi:10.1002/(SICI)1521-4141(199911)29:11<3596::AID-IMMU3596>3.0.CO;2-Y. PMID 10556814. 
  9. ^ Lee KM, Chuang E, Griffin M, Khattri R, Hong DK, Zhang W, Straus D, Samelson LE, Thompson CB, Bluestone JA (1998). "Molecular basis of T cell inactivation by CTLA-4". Science 282 (5397): 2263–6. PMID 9856951. 
  10. ^ Qureshi OS, Zheng Y, Nakamura K, Attridge K, Manzotti C, Schmidt EM, Baker J, Jeffery LE, Kaur S, Briggs Z, Hou TZ, Futter CE, Anderson G, Walker LS, Sansom DM (2011). "Trans-endocytosis of CD80 and CD86: a molecular basis for the cell-extrinsic function of CTLA-4". Science 332 (6029): 600–3. doi:10.1126/science.1202947. PMC 3198051. PMID 21474713. 
  11. ^ Knieke K, Lingel H, Chamaon K, Brunner-Weinzierl MC (2012). "Migration of Th1 lymphocytes is regulated by CD152 (CTLA-4)-mediated signaling via PI3 kinase-dependent Akt activation". PLoS ONE 7 (3): e31391. doi:10.1371/journal.pone.0031391. PMC 3295805. PMID 22412835. 
  12. ^ Schneider H, Downey J, Smith A, Zinselmeyer BH, Rush C, Brewer JM, Wei B, Hogg N, Garside P, Rudd CE (September 2006). "Reversal of the TCR stop signal by CTLA-4". Science 313 (5795): 1972–5. doi:10.1126/science.1131078. PMID 16931720. 
  13. ^ Rudd CE, Taylor A, Schneider H (May 2009). "CD28 and CTLA-4 coreceptor expression and signal transduction". Immunol. Rev. 229 (1): 12–26. doi:10.1111/j.1600-065X.2009.00770.x. PMID 19426212. 
  14. ^ Fife BT, Pauken KE, Eagar TN, Obu T, Wu J, Tang Q, Azuma M, Krummel MF, Bluestone JA (November 2009). "Interactions between PD-1 and PD-L1 promote tolerance by blocking the TCR-induced stop signal". Nat. Immunol. 10 (11): 1185–92. doi:10.1038/ni.1790. PMC 2778301. PMID 19783989. 
  15. ^ Simpson TR, Li F, Montalvo-Ortiz W, Sepulveda MA, Bergerhoff K, Arce F, Roddie C, Henry JY, Yagita H, Wolchok JD, Peggs KS, Ravetch JV, Allison JP, Quezada SA (2013). "Fc-dependent depletion of tumor-infiltrating regulatory T cells co-defines the efficacy of anti-CTLA-4 therapy against melanoma". J. Exp. Med. 210 (9): 1695–710. doi:10.1084/jem.20130579. PMC 3754863. PMID 23897981. 
  16. ^ Arthritis Research & Therapy | Meeting Abstract | Abatacept (CTLA4Ig) treatment increases the remission rate in rheumatoid arthritis patients refractory to methotrexate treatment
  17. ^ Pardoll DM (April 2012). "The blockade of immune checkpoints in cancer immunotherapy". Nat. Rev. Cancer 12 (4): 252–64. doi:10.1038/nrc3239. PMID 22437870. 
  18. ^ Follows ER, McPheat JC, Minshull C, Moore NC, Pauptit RA, Rowsell S, Stacey CL, Stanway JJ, Taylor IW, Abbott WM (October 2001). "Study of the interaction of the medium chain mu 2 subunit of the clathrin-associated adapter protein complex 2 with cytotoxic T-lymphocyte antigen 4 and CD28". Biochem. J. 359 (Pt 2): 427–34. doi:10.1042/0264-6021:3590427. PMC 1222163. PMID 11583591. 
  19. ^ Chuang E, Alegre ML, Duckett CS, Noel PJ, Vander Heiden MG, Thompson CB (July 1997). "Interaction of CTLA-4 with the clathrin-associated protein AP50 results in ligand-independent endocytosis that limits cell surface expression". J. Immunol. 159 (1): 144–51. PMID 9200449. 
  20. ^ Peach RJ, Bajorath J, Naemura J, Leytze G, Greene J, Aruffo A, Linsley PS (September 1995). "Both extracellular immunoglobin-like domains of CD80 contain residues critical for binding T cell surface receptors CTLA-4 and CD28". J. Biol. Chem. 270 (36): 21181–7. doi:10.1074/jbc.270.36.21181. PMID 7545666. 
  21. ^ Stamper CC, Zhang Y, Tobin JF, Erbe DV, Ikemizu S, Davis SJ, Stahl ML, Seehra J, Somers WS, Mosyak L (March 2001). "Crystal structure of the B7-1/CTLA-4 complex that inhibits human immune responses". Nature 410 (6828): 608–11. doi:10.1038/35069118. PMID 11279502. 
  22. ^ Baroja ML, Vijayakrishnan L, Bettelli E, Darlington PJ, Chau TA, Ling V, Collins M, Carreno BM, Madrenas J, Kuchroo VK (May 2002). "Inhibition of CTLA-4 function by the regulatory subunit of serine/threonine phosphatase 2A". J. Immunol. 168 (10): 5070–8. doi:10.4049/jimmunol.168.10.5070. PMID 11994459. 

Further reading[edit]

  • Liossis SN, Sfikakis PP, Tsokos GC (1998). "Immune cell signaling aberrations in human lupus.". Immunol. Res. 18 (1): 27–39. doi:10.1007/BF02786511. PMID 9724847. 
  • Chang TT, Kuchroo VK, Sharpe AH (2002). "Role of the B7-CD28/CTLA-4 pathway in autoimmune disease.". Curr. Dir. Autoimmun. 5: 113–30. doi:10.1159/000060550. PMID 11826754. 
  • Alizadeh M, Babron MC, Birebent B, Matsuda F, Quelvennec E, Liblau R, Cournu-Rebeix I, Momigliano-Richiardi P, Sequeiros J, Yaouanq J, Genin E, Vasilescu A, Bougerie H, Trojano M, Martins Silva B, Maciel P, Clerget-Darpoux F, Clanet M, Edan G, Fontaine B, Semana G (2003). "Genetic interaction of CTLA-4 with HLA-DR15 in multiple sclerosis patients". Ann. Neurol. 54 (1): 119–22. doi:10.1002/ana.10617. PMID 12838528. 
  • Chistiakov DA, Turakulov RI (2004). "CTLA-4 and its role in autoimmune thyroid disease". J. Mol. Endocrinol. 31 (1): 21–36. doi:10.1677/jme.0.0310021. PMID 12914522. 
  • Vaidya B, Pearce S (2004). "The emerging role of the CTLA-4 gene in autoimmune endocrinopathies". Eur. J. Endocrinol. 150 (5): 619–26. doi:10.1530/eje.0.1500619. PMID 15132716. 
  • Brand O, Gough S, Heward J (2007). "HLA , CTLA-4 and PTPN22 : the shared genetic master-key to autoimmunity?". Expert Reviews in Molecular Medicine 7 (23): 1–15. doi:10.1017/S1462399405009981. PMID 16229750. 
  • Kavvoura FK, Akamizu T, Awata T, Ban Y, Chistiakov DA, Frydecka I, Ghaderi A, Gough SC, Hiromatsu Y, Ploski R, Wang PW, Ban Y, Bednarczuk T, Chistiakova EI, Chojm M, Heward JM, Hiratani H, Juo SH, Karabon L, Katayama S, Kurihara S, Liu RT, Miyake I, Omrani GH, Pawlak E, Taniyama M, Tozaki T, Ioannidis JP (2007). "Cytotoxic T-lymphocyte associated antigen 4 gene polymorphisms and autoimmune thyroid disease: a meta-analysis". J. Clin. Endocrinol. Metab. 92 (8): 3162–70. doi:10.1210/jc.2007-0147. PMID 17504905. 

This article incorporates text from the United States National Library of Medicine, which is in the public domain.