Lack of correlation between the levels of soluble cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) and the CT-60 genotypes.
BACKGROUND
Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) plays a critical role in downregulation of antigen-activated immune response and polymorphisms at the CTLA-4 gene have been shown to be associated with several autoimmune diseases including type-1 diabetes (T1D). The etiological mutation was mapped to the CT60-A/G single nucleotide polymorphism (SNP) that is believed to control the processing and production of soluble CTLA-4 (sCTLA-4).


METHODS
We therefore determined sCTLA-4 protein levels in the sera from 82 T1D patients and 19 autoantibody positive (AbP) subjects and 117 autoantibody negative (AbN) controls using ELISA. The CT-60 SNP was genotyped for these samples by using PCR and restriction enzyme digestion of a 268 bp DNA segment containing the SNP. Genotyping of CT-60 SNP was confirmed by dye terminating sequencing reaction.


RESULTS
Higher levels of sCTLA-4 were observed in T1D (2.24 ng/ml) and AbP (mean = 2.17 ng/ml) subjects compared to AbN controls (mean = 1.69 ng/ml) with the differences between these subjects becoming significant with age (p = 0.02). However, we found no correlation between sCTLA-4 levels and the CTLA-4 CT-60 SNP genotypes.


CONCLUSIONS
Consistent with the higher serum sCTLA-4 levels observed in other autoimmune diseases, our results suggest that sCTLA-4 may be a risk factor for T1D. However, our results do not support the conclusion that the CT-60 SNP controls the expression of sCTLA-4.
Purohit
Sharad
S
Center for Biotechnology and Genomic Medicine, Medical College of Georgia, CA4095 Augusta, GA 30912.
Podolsky
Robert
R
Center for Biotechnology and Genomic Medicine, Medical College of Georgia, CA4095 Augusta, GA 30912.
Collins
Christin
C
Center for Biotechnology and Genomic Medicine, Medical College of Georgia, CA4095 Augusta, GA 30912.
Zheng
Weipeng
W
Center for Biotechnology and Genomic Medicine, Medical College of Georgia, CA4095 Augusta, GA 30912.
Schatz
Desmond
D
Department of Pediatrics, University of Florida, Gainesville FL 32607, USA.
Muir
Andy
A
Center for Biotechnology and Genomic Medicine, Medical College of Georgia, CA4095 Augusta, GA 30912.
Hopkins
Diane
D
Center for Biotechnology and Genomic Medicine, Medical College of Georgia, CA4095 Augusta, GA 30912.
Huang
Yi-Hua
YH
Center for Biotechnology and Genomic Medicine, Medical College of Georgia, CA4095 Augusta, GA 30912.
She
Jin-Xiong
JX
Center for Biotechnology and Genomic Medicine, Medical College of Georgia, CA4095 Augusta, GA 30912.