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Cytokine gene polymorphisms in autoimmune thyroid disease.
P J Hunt1, S E Marshall, A P Weetman
1Department of Endocrinology, Radcliffe Infirmary, Oxford, United Kingdom.
The Journal of Clinical Endocrinology and Metabolism
|June 8, 2000
Summary
A specific variant in the interleukin-4 (IL-4) gene appears to offer modest protection against autoimmune thyroid diseases like Graves' disease. This finding may offer new insights into the development of these conditions.
Area of Science:
- Immunogenetics
- Endocrinology
- Molecular Biology
Background:
- Autoimmune thyroid diseases (AITD), including Graves' disease (GD) and autoimmune hypothyroidism (AIH), result from complex genetic and environmental interactions.
- While human leukocyte antigen and cytotoxic T lymphocyte-associated-4 regions are implicated, other genetic factors remain largely unknown.
- Cytokines are key regulators of immune responses, making their genes potential candidates for AITD susceptibility.
Purpose of the Study:
- To investigate the association between polymorphisms in nine cytokine genes and susceptibility to AITD.
- To identify specific genetic variations that may contribute to the development of Graves' disease and autoimmune hypothyroidism.
Main Methods:
- A case-control study was conducted with 215 AITD patients (138 GD, 77 AIH) and 101 healthy controls.
- Genotyping of 15 polymorphisms in genes including IL-1alpha, IL-1beta, IL-4, IL-6, IL-10, and TGF-beta was performed using PCR and sequence-specific primers.
- Statistical analysis, including corrected P-values and odds ratios, was used to assess associations.
Main Results:
- A significantly reduced frequency of the variant 't' allele in the interleukin-4 (IL-4) promoter polymorphism (position 590) was observed in GD patients and the overall AITD group compared to controls (Pc < 0.00001).
- This reduction was reflected in a lower frequency of the c/t heterozygote genotype in AITD patients (11-12%) versus controls (23%), indicating a protective effect (odds ratio = 0.4).
- No significant associations were found for other cytokine gene polymorphisms, and subgroup analyses did not link variations to clinical disease parameters.
Conclusions:
- The study suggests that a specific IL-4 gene variant confers a modest protective effect against the development of autoimmune thyroid disease, particularly Graves' disease.
- This genetic variation in IL-4 may provide crucial insights into the pathogenesis of AITD and other organ-specific autoimmune disorders.
- Subtle variations in immunoregulatory genes could be associated with autoimmune disease states, warranting further investigation.