Objective: Programmed cell death-1 (PD-1) and its ligands (PD-L1 and PD-L2) inhibit T-cell proliferation and activation. This inhibition down-regulates the immune responses. The association of a PD-L1 polymorphism with Graves' disease (GD) was studied.
Design: The association of an A/C polymorphism at position 8923 in PD-L1 intron 4 with GD was studied.
Patients: The study included 327 GD patients and 192 controls, of which 252 GD patients were followed over 5-10 years.
Measurements: PD-L1 intron 4 position 8923 A/C polymorphism was typed using the PCR-restriction fragment length polymorphism method.
Results: The A/C genotype frequencies were significantly different between GD patients and controls. The A/C and C/C frequencies were higher in GD patients than in controls. The A/A frequencies were lower in GD patients than in controls. C-allele frequency was higher in GD patients than in controls. A total of 252 GD patients were followed over 5-10 years; 200 had discontinued antithyroid drugs (ATD) while 52 continued to take ATD. Of these 200, 176 continued to be in remission and 24 had relapsed into hyperthyroidism. Significant differences in the duration of positive TBII, positive thyroid-stimulating antibodies, and ATD treatment were noted between the patients in remission and those that had relapsed. Significant differences in the A- and C-allele frequencies were noted between the two. The C-allele frequency was higher in GD patients who did not achieve remission than in those who achieved remission.
Conclusion: An A/C polymorphism at position 8923 in PD-L1 is associated with GD. The PD-L1 polymorphism plays a role in GD development. GD patients with the C allele at position 8923 in PD-L1 gene had difficulty in achieving remission.