Introduction
The main role of forkhead box P3 (FOXP3) + regulatory T (Treg) cells is to maintain immune tolerance and prevent inflammatory diseases [1]. The impaired function and/or homeostasis of these cells has been implied in the development of several autoimmune and inflammatory diseases, including rheumatoid arthritis, lupus erythematosus, multiple sclerosis and type 1 diabetes [2]. A growing evidence suggests that the defect within Treg compartment might also be an underlying cause of an inflammatory bowel disease (IBD), a chronic relapsing and remitting inflammatory gastrointestinal tract condition [3]. The disease manifests as two distinct but often overlapping clinical forms – ulcerative colitis (UC), which pathology is restricted to the colonic mucosa, and Crohn’s disease (CD), which can affect any part of the gastrointestinal tract [4]. Our project aimed to investigate the levels of peripheral CD4+CD25+FOXP3+ Tregs in patients with active moderate-to-severe UC.
Material and methods
The project was approved by the local Ethics Committee. A group of 40 adults with active moderate-to-severe UC comprising 27 females (67.5%) and 13 males (32.5%) of a mean age of 34.2 ±13.1 years was enrolled. The disease had been diagnosed and confirmed by endoscopic means. Only patients with CRP level 10 mg/ml were eligible. Only patients treated with conventional therapies, including 5-aminosalicylates, prednisolone, budesonide, azathioprine, mercaptopurine, methotrexate and antibiotics, were recruited to the study. The control group was composed of 15 healthy volunteers, 9 females (60%) and 6 males (40%) of a mean age of 31.6 ±9.2 years that had not been subject to any immunomodulatory therapies. A cytometric analysis was performed to evaluate the levels of CD4+CD25+FOXP3+ regulatory T cells (BioLegend, USA) in peripheral blood of the investigated patients. Also, serum samples were cytometrically tested for concentrations of interleukin 10 (IL-10) (BD Biosciences Pharmingen, USA). The data were analyzed by Mann-Whitney U, a Wilcoxon signed rank test, and 2 test using SPSS version 15. Values were considered significant when p < 0.05.
Results
A statistical analysis showed a significant difference in the levels of peripheral CD4+CD25+FOXP3+ regulatory T cells among the investigated groups. A significantly lower percentage of Tregs was found in the active moderate-to-severe UC group compared with the control group (1.32 ±0.7 vs. 2.36 ±1.4; p < 0.05) (Fig. 1). No significant difference in the mean levels of serum IL-10 was observed among the investigated groups (p > 0.05).
Discussion
Our analysis showed a lower percentage of CD4+CD25+FOXP3+ Tregs in peripheral blood of the UC patients compared with the control group, which is consistent with some reports [3, 5]. The lower percentage of Tregs might result from the numerical and/or functional defect of these cells, which has been implicated in the development of several autoimmune and inflammatory diseases [1]. It is possible that the generation and function of these cells are inhibited by a chronic overproduction of IL-6 and IL-17 found in UC patients [6]. Active blocking by Th17 cells, which stay in a dynamic balance with Treg compartment, is another possibility [7]. Current data demonstrate that active UC is characterized by a numerical defect of regulatory T cell subpopulation rather than by a compromised suppressor function of these cells. In spite of their presence in the inflamed GI tract of CD patients, their number is probably insufficient to control the ongoing inflammation [3]. It is worth noting that the low percentage of peripheral Tregs found in the active moderate-to-severe UC patients is accompanied by normal serum levels of IL-10. Interleukin 10 is a potent anti-inflammatory and immunoregulatory cytokine produced mainly by Tregs and its presence appears to be required for suppression of colitis in mouse models [8, 9]. Normal, but not elevated, levels of IL-10 in the serum of UC patients might also suggest the numerical defect of Tregs. Concluding, Tregs have a potent anti-inflammatory capacity in animal models of colitis. It seems that patients with active moderate-to-severe UC also exhibit a numerical dysfunction within Treg compartment. Therefore, further research is needed to evaluate the potential of Treg adoptive transfer method for UC treatment.
References
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