CTLA4 rs231775: What Your Genotype Means
The rs231775 variant is a common genetic change in the CTLA4 gene that alters a single amino acid in the resulting protein. It is frequently studied for its potential role in modulating immune system activity and its statistical association with several autoimmune conditions.
What each genotype means
Baseline CTLA-4 expression
This genotype represents the ancestral or wild-type form of the CTLA4 gene at this position. Research suggests this version may be associated with higher cell-surface expression of the CTLA-4 protein compared to the G allele, which is involved in regulating T-cell activity.
This genotype is common in many populations, though its frequency varies significantly by ancestry, being more prevalent in European populations compared to East Asian populations.
Intermediate CTLA-4 expression
Carrying one copy of the G allele may result in intermediate levels of CTLA-4 cell-surface expression. Some studies suggest that individuals with this genotype may have a slightly different susceptibility profile for certain autoimmune conditions compared to those with the AA genotype, though findings across different populations remain inconsistent.
This is a very common heterozygous genotype found globally, with frequencies reflecting the high prevalence of the G allele in many human populations.
Reduced CTLA-4 expression
This genotype is associated with a functional change (p.Thr17Ala) that can lead to reduced CTLA-4 cell-surface expression. Research has linked this variant to an increased statistical risk for certain T-cell-mediated autoimmune disorders, such as rheumatoid arthritis, systemic lupus erythematosus, and type 1 diabetes, though the clinical impact varies by individual and population.
The G allele is highly common, with frequencies exceeding 0.60 in East Asian ancestries and ranging from 0.35 to 0.40 in European ancestries, making this genotype frequently observed.
Understanding the rs231775 Variant
The rs231775 variant, often referred to as the +49A>G polymorphism, is a single-nucleotide polymorphism (SNP) located in the first exon of the CTLA4 gene on chromosome 2. This specific change involves the substitution of an adenine (A) base for a guanine (G) base. At the protein level, this genetic variation results in a missense mutation where the amino acid threonine is replaced by alanine at position 17. Because this change occurs in a functional region of the gene, researchers have long investigated whether it impacts the structure or efficiency of the CTLA-4 protein. Genetic variants like this are common in the human population, and they serve as important markers for understanding how subtle differences in our DNA can influence biological processes, such as the fine-tuning of immune responses.
The Role of the CTLA4 Gene
The CTLA4 gene encodes the Cytotoxic T-Lymphocyte Associated Protein 4, a critical protein that acts as an 'off switch' for the immune system. Under normal conditions, T-cells—the white blood cells responsible for identifying and attacking pathogens—must be carefully regulated to prevent them from damaging the body's own healthy tissues. CTLA-4 is expressed on the surface of activated T-cells, where it competes with other receptors to dampen or inhibit the immune response. By limiting T-cell activation, CTLA-4 helps maintain immune tolerance and prevents the development of autoimmunity. When the function or expression of this protein is altered, the immune system may become hyper-reactive, potentially increasing the risk of the body mistakenly attacking its own cells, which is a hallmark of various autoimmune disorders.
Research and Associations
Scientific literature has explored the association between the rs231775 variant and a wide range of autoimmune conditions, including Hashimoto thyroiditis, Graves' disease, type 1 diabetes, and rheumatoid arthritis. Some studies suggest that the G allele may lead to reduced cell-surface expression of the CTLA-4 protein, potentially impairing its inhibitory function. However, the evidence is mixed and often varies significantly by ancestry and geographic population. While some meta-analyses have identified statistically significant associations with disease risk, other studies have found no such link in different cohorts. It is important to note that these associations are statistical in nature, meaning the presence of a specific genotype does not guarantee the development of a disease. Autoimmune conditions are complex and typically result from a combination of multiple genetic factors, environmental triggers, and lifestyle influences.
Population Frequency
The distribution of the rs231775 variant varies across global populations. The minor allele (G) is relatively common, with frequencies typically ranging from approximately 0.35 to 0.40 in European ancestries and exceeding 0.60 in many East Asian populations. Because this variant is so prevalent, it is considered a common genetic polymorphism rather than a rare mutation. Researchers often use these frequency differences to study how evolutionary pressures or population history might influence the prevalence of immune-related traits in different parts of the world.
Interpreting Your Genetic Information
If you have access to your genetic data regarding the rs231775 variant, it is important to view this information in the proper context. Genetic testing for this SNP is not a diagnostic tool for any autoimmune disease. Because the association between this variant and health outcomes is limited and inconsistent across different studies, it cannot be used to predict your personal risk of developing a specific condition. If you have concerns about your immune health or a family history of autoimmune disorders, the most appropriate step is to consult with a healthcare professional or a genetic counselor. They can help you interpret your health history and determine if any clinical testing is necessary. Never use genetic data to make decisions about your health, medications, or lifestyle without professional medical guidance.
How common is this variant?
The minor allele (G) frequency ranges from approximately 0.35–0.40 in European ancestries to over 0.60 in East Asian populations.
Frequently asked questions
Does having the GG genotype mean I will get an autoimmune disease?
No. The presence of the GG genotype is only a statistical association found in some research studies and does not mean you will develop a disease. Autoimmune conditions are complex and involve many genetic and environmental factors.
Can I change my risk associated with this SNP?
You cannot change your genotype. However, maintaining a healthy lifestyle and discussing your family medical history with a doctor are the best ways to manage your overall health and address any concerns about autoimmune conditions.
Is rs231775 the same as the CT60 polymorphism?
No, they are different SNPs. While both are located in the CTLA4 gene region and are studied in the context of autoimmune disease, they represent different genetic variations.
Should I get tested for this variant?
There is generally no clinical utility in testing for this specific variant. It is not used for routine diagnosis or treatment planning, and you should discuss any health concerns with your primary care physician.
Sources & further reading
Educational information only, last refreshed 9/21/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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