CTLA-4 and autoimmune thyroid disease: lack of influence of the A49G signal peptide polymorphism on functional recombinant human CTLA-4.
A single nucleotide A49G polymorphism (SNP) of CTLA-4 has been linked and associated with the autoimmune thyroid diseases (AITD) and thyroid autoantibody secretion. We have explored the functional mechanisms of CTLA-4 by means of recombinant human CTLA-4 expressed on transfected Jurkat T cells. Analysis of CTLA-4 transcripts with quantitative real-time PCR demonstrated similar baseline and PHA-stimulated levels for both the A49 and G49 alleles, which were markedly enhanced by anti-CTLA-4 engagement. Both alleles also coded for proteins which were expressed on the cell membrane, as measured by FACS analysis using anti-CTLA-4 (G: 34.4+/-11.9% cells, A: 27.6+/-8.6% cells) (p=ns). Baseline and PHA-stimulated IL-2 production were also similar among control and CTLA-4 clones expressing both alleles. After anti-CTLA-4 engagement, IL-2 production was markedly inhibited in a dose- and time-dependent manner but this also appeared to be similar in the A and G allele expressing cells (95.7+/-1.2% inhibition and 94.9+/-1.1% inhibition, respectively). In conclusion, both the extrinsic and intrinsic actions of human CTLA-4 were not affected by the signal peptide A49G polymorphism. Therefore, the linkage of the CTLA-4 A49G SNP to AITD is most likely secondary to linkage disequilibrium.
Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA.
Yang
Y
Xu
Peter N
PN
Graves
Yaron
Y
Tomer
Terry F
TF
Davies
D000069594:Abatacept; D000483:Alleles; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000378:metabolism; D000941:Antigens / Q000276:immunology / Q000378:metabolism; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D060908:CTLA-4 Antigen; D002469:Cell Separation; D005434:Flow Cytometry; D017930:Genes, Reporter; D006801:Humans; D018796:Immunoconjugates; D007141:Immunoglobulin Fc Fragments / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007166:Immunosuppressive Agents / Q000276:immunology / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D019169:Jurkat Cells; D020641:Polymorphism, Single Nucleotide; D021382:Protein Sorting Signals / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D013967:Thyroiditis, Autoimmune / Q000235:genetics / Q000276:immunology* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000941:Antigens; D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D018796:Immunoconjugates; D007141:Immunoglobulin Fc Fragments; D007166:Immunosuppressive Agents; D007376:Interleukin-2; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D000069594:Abatacept