RESUMO
Background: Type 1 diabetes [T1D] is a T cell mediated autoimmune disease targetingthe insulin-producing beta cells within pancreatic islets. Autoimmune diseases maydevelop as a consequence of altered balance between regulatory [Tregs] andautoreactive T cells
Objectives: To evaluate Treg cells frequency and suppressivefunction in the peripheral blood of newly diagnosed T1D patients in comparison withhealthy controls
Methods: Fifteen new cases of T1D patients and 15 age- and sexmatchedhealthy controls were recruited to this study. Their peripheral bloodmononuclear cells [PBMCs] were isolated and CD4[+]CD25[+]FoxP3[+]CD127[-/low] Treg cellswere studied by flowcytometry technique. Thereafter, Tregs were isolated by Magnetic-Activated Cell Separation [MACS] technology and by using CFSE [carboxyfluoresceinsuccinimidyl ester] dilution assay, their suppressive activity was evaluated in thecoculture of CD4[+]CD25[-] T responder cells with Treg cells
Results: The percentage ofCD4[+]CD25[+]FoxP3[+]CD127[-/low] Tregs did not differ between T1D patients and healthycontrols but the MFI [mean fluorescence intensity] of transcription factor FoxP3[forkhead box protein P3] was significantly decreased in T1D patients [20.03 +/- 1.4 vs.31.33 +/- 2.95, p=0.0017]. Moreover, the suppressive function of CD4[+]CD25[+]CD127[-/low]Treg cells was significantly diminished in T1D patients in comparison with controlgroup [35.16 +/- 4.93% vs. 60.45 +/- 5.26%, respectively, p=0.0015]
Conclusion: Presentstudy indicates an impaired immune regulation among T1D patients, characterized bydefects in suppressive function and expression of FoxP3 in Treg cells without anysignificant decrease in their frequency in peripheral blood
RESUMO
Type-I diabetes is an autoimmune inflammatory disease in which pancreatic beta-cells are selectively destroyed by infiltrating cells. TNF-related apoptosis-inducing ligand [TRAIL] is a type-II membrane protein of the TNF superfamily which is expressed in different tissues, including pancreas and lymphocytes. In humans, TRAIL interacts with four membrane receptors. TRAIL-R1 and TRAIL-R2 have cytoplasmic death domains, and can activate both caspases and NF?B pathways. The other two receptors, TRAIL-R3 and TRAIL-R4, are decoy receptors not capable of activating caspase cascade but may activate NF-?B and block apoptosis. As human beta cells are sensitive to TRAIL induced apoptosis, signaling via these molecules is considered to be a probable way of beta cell destruction. These molecules also are important in suppression of autorective T cells and immunoregulation. To explore the importance of TRAIL and its receptors at pathogenesis of type-I diabetes, we compared expression of these molecules on T-cells of diabetic patients and healthy controls. In this study, expression of TRAIL and its receptors at protein and mRNA levels were studied in freshly isolated peripheral T cells of 55 type I diabetic patients and 50 healthy individuals by flowcytometry, western blot and RT-PCR. We found that expression of TRAIL and its receptors in peripheral T-cells at both protein and mRNA levels are significantly increased in patients [except for TRAIL-R2 mRNA which was slightly higher in controls] but increase in TRAIL, TRAILR3 [2.7% vs. >0.5%] and TRAIL-R4 [2.6% vs. >0.5%] is more considerable. sTRAIL in sera of patients was significantly lower than in controls [p=0.01]. Our results explain resistance of autoreactive T-cells to immunoregulatory mechanisms. Besides, increased expression of TRAIL in autoreactive T-cells may play an important role in betacell destruction. Lower level of sTRAIL in diabetic patients may be a reason for hyperactivation of autoreactive T-cells