[Polymorphisms of MICA microsatellites in thyroidal autoimmunity].
BACKGROUND
The autoimmune thyropathies Graves' disease (GD) and Hashimoto's thyroiditis (HT) have multiple genetic and environmental backgrounds. Allele alterations of immune genes might contribute to the development of autoimmunity.


METHODS
This study determined a triplet short tandem repeat (STR) polymorphism in the transmembrane region of the major histocompatibility complex (MHC) class I chain-related gene A (MICA) of 391 subjects (129 patients with GD, 56 patients with HT, and 206 healthy controls). Five common alleles have been reported for MICA. Genotypes were determined by fragment-length analysis in an ABI PRISM automatic sequencer.


RESULTS
The prevalence of the MICA allele A9 was raised in patients with HT compared to controls (22.4% vs. 13.1%; p = 0.016; Fisher's exact test). For MICA, the genotype A5.1/A5.1 occurred more frequently in patients with GD than in controls (24.0% vs. 13.6%, odds ratio [OR] = 2.0, 95% confidence interval [95% CI] = 1.1-3.6; p = 0.018). The genotype MICA A6/A9 was decreased in patients with GD in contrast to controls (1.6% vs. 5.8%, OR = 0.2, 95% CI = 0.6-1.2; p = 0.089). Also, in patients with HT, the genotype A5.1/A9 was increased compared to controls (23.2% vs. 10.7%, OR = 2.5, 95% CI = 1.2-5.4; p = 0.025).


CONCLUSIONS
The genotype MICA A5.1/A5.1 may be regarded as a risk factor for the development of GD. Also, the MICA genotype A5.1/A9 could raise the risk for acquiring HT. Finally, the genotype MICA A6/A9 could be seen as a protective factor against GD.
Ide
Maximilian
M
I Medizinische Klinik und Poliklinik, Johannes Gutenberg-Universität Mainz, 55101 Mainz.
Dittmar
Manuela
M
Wurm
Michael
M
Kanitz
Michael
M
Kahaly
George J
GJ
D000328:Adult; D000368:Aged; D000483:Alleles; D002896:Chromosomes, Human, Pair 6; D005260:Female; D005787:Gene Frequency / Q000235:genetics; D005838:Genotype; D006111:Graves Disease / Q000235:genetics*; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D011110:Polymorphism, Genetic / Q000235:genetics*; D013967:Thyroiditis, Autoimmune / Q000235:genetics*; D018911:Trinucleotide Repeats
D015395:Histocompatibility Antigens Class I; C099187:MHC class I-related chain A