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.
Xu
Yang
Y
Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA.
Graves
Peter N
PN
Tomer
Yaron
Y
Davies
Terry F
TF
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