Study On The Role Of NK Cells And Its Receptors In Graves’ Diseases

Background: Graves’ disease(GD) is a frequent organ-specific autoimmune thyroid disease with prevalence 1. 2%. GD is typically characterized by the presence of circulating autoantibodies that bind to and stimulate the thyroid hormone receptor(TSHR), resulting in hyperthyroidism and goiter. As in most autoimmune diseases,GD is more frequent in women than in men, with a ratio of approximately 4-6/1. In1988 MR. Karlsson and MR. Tezuka have found a decreased percentage of NK cell in peripheral blood from hyperthyroid GD patients. Moreover, GD patients who were hypothyroid after radioactive iodine therapy or thyroidectomy had normal NK activity.NK cells are large granular cells with the ability to lyse target cells and provide an early source of immunoregulatory cytokines. Human NK cells represent a minor fraction, 2% to 18%, of total lymphocytes in human peripheral blood, and are defined by CD56 positive CD3 negative characteristics. NK cells are effector lymphocytes of the innate immune system and play an important role in bridging the innate and adaptive immune responses as immune regulatory cells. But, the role that NK cells plays in the pathogenesis of Graves’ disease remain unclear. This study explored the presence of activated and inhibitory receptors of NK and NKT cells in the peripheral blood of patients with new GD onset.Methods: A total of 28 patients with new onset GD were recruited from the outpatient service of the First Hospital of Jilin University, between December 2011 and November 2013. Individual patients with GD were diagnosed according to the clinical evidence of hyperthyroidism(thyroid stimulating hormone, TSH < 0.3 u IU/L,normal range: 0.3–3.6 pmol/L; free triiodothyronine(FT3) > 6.5 pmol/L, normal range: 3.5–6.5 pmol/L; and free thyroxine(FT4) > 22.7 pmol/L, normal range:11.5–22.7 pmol/L), the presence of anti-TSHR antibodies(normal range: 0.3-1.22IU/L), and diffuse goiter, as investigated by ultrasound examination. 23 healthy volunteers, whose gender and age were matched with GD patients, without a family history of GD were recruited from the outpatient service of the same hospital and served as controls. Individual participants were excluded if she/he had current or history of other autoimmune diseases, such as T1 D, RA, SLE, multiple sclerosis and autoimmune hepatitis, or other chronic inflammatory diseases, such as metabolic syndrome, inflammatory bowel disease, and chronic renal disease. A clear explanation of the objectives and the implications of the results were given to each participant;subsequently, each participant signed an institution-approved informed consent. The study was approved by the Institutional Ethics Board of School of Medicine, Jilin University. The demographic and clinical data of individual participants were collected from hospital records and reviewed by endocrinologists. The number of NK cells in peripheral blood of individual subjects was determined by flow cytometry.Results: 1. The number of peripheral blood CD3-CD56+NK cells(p=0.0107),CD3-CD16+NK cells(p=0.0067), CD3+CD56+ NKT cells(p=0.0017) and CD3+CD16+ NKT cells(p=0.0012) was significantly decreased in the GD patients compared to the healthy controls.2. In our study, we found that significantly decreased number of NKG2D+(p=0.0099), NKG2C+(p=0.0120), NKG2A+(p<0.0001) and NKp30+(p=0.0114) NK cells, but increased numbers of KIR3DL1+(p=0.0119) NK cells in the GD patients compared to the HC(Fig.2). But there was no significant difference in the number of peripheral blood NKp44+, NKp46+, KIR2DL3+, CD158a+ and CD158b+ NK cellsbetween the patients and controls.3. In our study, the number of inducible CD107a+(p=0.0278) and IFN- ?-secreting NK cells(p<0.0001) in GD patients decreased significantly compared to the controls(Fig.3). But there was no significant difference in the number of spontaneous IFN-γ and CD107a+ NK cells between GD and HC.4. The number of CD3-CD56+(p=0.0481 r=0.3768), CD3-CD16+(p=0.0086r=0.4870) and NKG2D+NK cells(p=0.0039 r=0.5275) was negatively correlated with the levels of serum FT4 in GD patients(Fig.4). Moreover, the number of KIR3DL1+NK cells(p=0.0028 r=0.5439) was negatively correlated with the levels of serum FT4 in GD patients.5. Interestingly, we found that the number of KIR3DL1+ NK cells(p=0.0037r=0.5302) was positively correlated with the levels of serum auto antibodies to thyroid peroxidase(A-TPO) in GD patients.The number of NKG2A+ NK cells(p=0.0220r=0.4311) was negatively correlated with the levels of serum TRAb in GD patients.Conclusion: 1. The number of peripheral blood NK cells was significantly decreased in the GD patients compared to the healthy controls.2. There are significantly decreased number of NKG2D+, NKG2C+ and NKp30+NK cells, but increased numbers of KIR3DL1+ NK cells in the GD patients compared to the HC.3. Impaired function of NK cell can be observed in GD patients.4. The number of NK cells was negatively correlated with the levels of serum FT4 in GD patients.5.The number of NKG2A+ NK cells was negatively correlated with the levels of serum TRAb in GD patients.