Due to an "immunological inexperience", the sensitivity of newborns to infectious diseases might be partially due to the lack of pre-existing immunological memory in newborns. After birth, T and B lymphocytes usually undergo a massive expansion in healthy newborns at term, probably due to an extensive antigenic stimulation from the environment. In preterm newborns, it is presumed that the immune system is less developed at birth, but little is known about the number and characteristics of lymphocyte subsets. Regulatory T cells (Tregs) have a crucial role in controlling the development of a healthy immune system including the maintenance of self-tolerance and, their lack, is responsible for a range of inflammatory and autoimmune manifestations observed in patients with IPEX (Immunodeficiency, Poliendocrinopathy and enteropathy X-linked syndrome). These cells are phenotypically characterized by the presence of the transcription factor Foxp3 (forkhead box P3) and the high expression of the ±-chain of IL-2 receptor (CD25), since this cytokine is essential for the generation, maintenance and function of Treg cells. In preliminary results from our group, it was observed greater ability of newborns to produce pro-inflammatory response when compared with adults, which was further accentuated by the apparent decrease in the production of IL-10, an important anti-inflammatory cytokine, which suggests a reduced regulatory function. Therefore, the objective of this study is to phenotypically characterize the population of regulatory T cells, as well as analyze their ability to produce IL-10 in term and preterm newborns of different gestational ages. The phenotypic characterization, using specific markers of regulatory T cells, as well as the intracellular staining of IL-10 in these cells will be performed by flow cytometry in umbilical cord blood from preterm newborns <34 weeks (Group 1), preterm newborns between e 34 and <37 weeks (Group 2) and from term newborns > 37 weeks (Group 3), being 15 samples per group, in comparison with healthy adults.
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