CTLA-4 −1661A/G and −658C/T gene polymorphisms in autoimmune thyroid diseases
Ileana Duncea1, Laura Crisan1, Radu Popp2, Carmen Georgescu1, Ioana Ilie1, Adrian Paul1, T Crisan2 & Cristian Brad
Genetic predisposition to autoimmunity is probably predominant. Major histocompatibility complex (MHC) alleles and non-MHC loci such as polymorphism of the cytotoxic T lymphocyte antigen-4 (CTLA4) gene have been identified as susceptibility markers. The autoimmune thyroid diseases are the most common organ-specific autoimmune diseases. They are characterized by the infiltration of the parenchyma by immune cells including T and B cells as well as macrophages. Ones a T cell is activated, it expresses proteins that transmit co-stimulatory signals to sustain or modify clonal expansion and differentiation. CTLA4 is a protein that inhibits co-stimulation. CTLA4 belongs to the immunological super family Ig and is also known as the molecule CD 152; it is expressed on T Helper surface and the CTLA4 gene was found on the chromosome 2q33. There are few studies regarding association between autoimmune thyroid diseases and polymorphisms of CTLA4 gene (+49A/G, CT 60). We aimed to investigate in a casecontrol study whether CTLA4 −1661A/G and/or −658C/T are involved in genetic predisposition to autoimmune thyroid diseases. Between January and April 2009 we observed 42 patients 21 diagnosed with Hashimotos thyroiditis or Gravess disease by specifics antibodies, 21 with no signs of autoimmunity. Written consent was obtained from patients. After the isolation of genomic DNA from peripheral blood mononuclear cells CTLA4 1661A/G and 658C/T gene polymorphisms were genotyped by restriction fragment length polymorphism and the data were statistical analyzed using SPSS program.
Results: Our results demonstrate a lack of association between CTLA-4 −1661A\G and −658C\T polymorphisms and autoimmune thyroid disorders. It was not statistically different between control group and patients group for both polymorphisms: −1661A\G (P=0.094), −658C\T (P=0.889).
Conclusion: Our study illustrates the necessity to include a large number of patients in genetic casecontrol studies and to investigate the association between these polymorphisms and other markers such as level of thyroid auto-antibodies.