Otoimmün hastalıklarda TREC (t-cell receptor excision circle)
krec (kappa- deleting recombination circle) analizi / Analysis of TREC (t-cell receptor excision circle) / krec (kappa- deleting recombination circle) in autoimmune diseases
Yazar: ÖZGE ŞAHİN KİMYON
Danışman: PROF. DR. MUHLİS CEM AR
İstanbul Üniversitesi-Cerrahpaşa / Cerrahpaşa Tıp Fakültesi / İç Hastalıkları Ana Bilim Dalı
Derece: Tıpta Uzmanlık, 2021
Konu: İç Hastalıkları = Internal diseases
Dizin: Hashimoto hastalığı = Hashimoto disease ; Otoimmün hastalıklar = Autoimmune diseases ; Otoimmünite = Autoimmunity ; T lenfositleri = T lymphocytes ; Tiroidit = Thyroiditis ; Trombositopeni = Thrombocytopenia

Özet:
Amaç: Otoimmünite patogenezine yönelik çalışmalarda, yeni T lenfosit üretimini ve gelişimini gösteren "T cell receptor excision circle (T hücre reseptörü eksizyon halkası-TREC)''; yeni B lenfosit üretimini ve gelişimini gösteren "Kappa-deleting recombination excision circle (Kappa-delesyon rekombinasyon eksizyon halkası-KREC)'' adı verilen belirteçlerin rol oynadığı ileri sürülmüştür. 
Çalışmamızın temel hedefi iki otoimmün hastalık grubunda [immün trombositopeni (İTP) ve Hashimoto tiroiditi (HT)]  çevresel kan TREC ve KREC düzeyinin sağlıklı kontrollerle karşılaştırılması ve hastalık süresi ile TREC ve KREC düzeyleri arasındaki ilişkinin incelenmesidir. Gereç ve Yöntem: Bu çalışmaya 45 HT,10 İTP tanılı hasta ile 39 sağlıklı gönüllü dahil edilmiştir. Çalışmaya katılanların çevresel kan örneğinden kantitatif polimeraz zincir reaksiyonu yöntemiyle TREC ve KREC kopya sayısı ölçüldü. Ayrıca HT'li grubun, lenfosit alt gruplarının analizi amacıyla çevresel kan örneğinden akış sitometri çalışıldı. 
Bulgular: HT, İTP grubu ve sağlıklı kontroller arasında TREC düzeyleri açısından fark saptanmazken (p= 0,684); KREC düzeyleri anlamlı düzeyde farklı saptandı. Bu fark HT'li gruptaki KREC düzeylerinin İTP ve kontrol grubuna göre daha yüksek bulunmasından kaynaklanmaktaydı (her ikisi için; p< 0.001).
HT alt grubunda KREC düzeylerinin hastalık süresi ≥5 yıl olanlarda anlamlı olarak daha düşük (p=0,046) olduğu görüldü. HT'li hastalarda KREC kopya sayısı ile çevresel kan lenfosit sayısı ve CD19+ lenfosit oranı pozitif korele saptandı.   
Sonuç: Çalışmamızda İTP hastalarında belirgin değişiklik görülmemesine karşın HT hastalarında KREC düzeylerinin yüksek olduğu; özellikle uzun süreli hastalık halinde bu düzeylerin düşme eğilimine girdiğini gösterdik. Daha homojen ve çok sayıda hasta ile sonuçların doğrulanmasına gereksinim vardır.

Abstract:
Objective: Autoimmunity is defined as the immune response against the organism's own antigens. In current studies on T and B lymphocyte-related immune mechanisms that have a role in the pathogenesis of autoimmune diseases, it is claimed that the markers called "T cell receptor excision ring (TREC)" showing T lymphocyte development and "Kappa-deletion recombination excision ring (KREC)" showing B lymphocyte development play a role. The T lymphocyte TREC copy number in the peripheral blood is assumed to be as an indirect indicator of the production of new T lymphocytes that have completed their maturation in the thymus, and the B lymphocyte KREC copy number is an indirect indicator of the level of new B lymphocytes that have completed their maturation in the bone marrow.
The two main objectives of our study are to compare the peripheral blood TREC and KREC copy numbers with healthy controls in two autoimmune disease groups [immune thrombocytopenia (ITP) and Hashimoto's thyroiditis (HT)] and to examine the relationship between disease duration and TREC and KREC levels.
Materials and Method: In this study, 94 adult individuals, including 45 HT patients followed up from Cerrahpaşa Faculty of Medicine, Department of Endocrinology, and 10 ITP patients followed up from Hematology Department, and 39 healthy volunteers of similar age and gender, without any known chronic disease, were included. TREC and KREC copy numbers were measured by quantitative polymerase chain reaction (PCR) method from peripheral blood samples of individuals in the patient and control groups. In addition, flow cytometry was performed from peripheral blood samples for the analysis of lymphocyte subgroups in patients with HT.
Results: KREC levels were found to be statistically different while there was no statistically significant difference in TREC levels between HT, ITP group and healthy controls (p= 0.684). This different is due to the fact that the KREC levels in patients with HT was higher than ITP and control group (p<0.001; for both).
There was no statistically significant difference between the subgroups in regarding gender in terms of TREC and KREC levels.
In the HT subgroup, the duration of the disease "less than 5 years" or "more than 5 years" had no effect on TREC levels (p=0.868); It was observed that KREC levels were significantly lower (p=0.046) in patients with disease duration ≥5 years. A positive correlation was found between KREC copy number and peripheral blood lymphocyte count and CD19+ lymphocyte ratio in patients with HT.
Conclusion: KREC and TREC can provide important data in terms of understanding the mechanism of autoimmune diseases and monitoring the efficacy of treatment. In our study, although no significant change was observed in ITP patients, KREC levels were high in HT patients; however, it was shown that these levels tend to decrease, especially in case of long-term illness. The reasons why no significant change was observed in the ITP group can be explained by the following: small number of patients, the heterogeneous physiopathology of the ITP disease, and the fact that the patients used steroids and/or immunosuppressive drugs at certain periods during the course of the disease, although not during the study. There is a need for a further research with more homogeneous and large number of patients to confirm the results of this very study.