Age-Related Differences in Percentages of Regulatory and Effector T Lymphocytes and Their Subsets in Healthy Individuals and Characteristic STAT1/STAT5 Signalling Response in Helper T Lymphocytes

The dynamic process of the development of the immune system can in itself result in age-related immune malfunctions. In this study, we analysed lymphocyte subsets in the peripheral blood of 60 healthy donors, divided into groups of children, adolescents, and adults, focusing on effector (Teff) and regulatory (Treg) T lymphocytes and STAT1/STAT5 signalling response in helper T lymphocytes (Th) in adults, using flow cytometry. Our results demonstrate a decrease in the percentage of total Tregs and an increase in the percentage of total Teffs with age and a consequential immense increase in the Teff/Treg ratio. The increase of Teffs was most apparent in Th1, Th1Th17, and Th17CD161− subsets. Significant Th lymphocyte STAT1 expression differences were observed between children and adolescents, which were associated with the decrease in activated Tregs. Higher expression of STAT1 was found in FoxP3hi than in FoxP3low Th lymphocytes, while significant IL-2 induced STAT5 phosphorylation differences were found among the subsets of Th lymphocytes in adults. Our study demonstrates age-related changes in circulating Teff and Treg, as well as significant differences in STAT5/STAT1 signalling among FoxP3+ Th lymphocytes, providing new advances in the understanding of immunosenescence.

Do studies in humans better depict Th17 cells?

CD4+ T helper (Th) lymphocytes represent a heterogeneous population of cells. In addition to type 1 (Th1) and type 2 (Th2) cells, another subset of CD4+ effector Th cells has been discovered and named as Th17, because of its unique ability to produce interleukin (IL)–17. Studies in mice initially suggested that Th17 cells are the pathogenic cells in autoimmune disorders, whereas Th1 cells may behave rather as protective. Subsequent studies in humans demonstrated the plasticity of Th17 cells and their possibility to shift to Th1. The plasticity of Th17 to Th1 cells has recently been confirmed in mice, where it was found that Th17 cells seem to be pathogenic only when they shift to Th1 cells. Studies in humans also showed that Th17 cells are different than in mice because all of them express CD161 and exclusively originate from CD161+ precursors present in umbilical cord blood and newborn thymus. While murine Th17 cells develop in response to IL-6, IL-1, and transforming growth factor (TGF)–β, human Th17 cells originate from these CD161+ precursors in response to IL-1β and IL-23, the need for TGF-β being controversial. Thus, we believe that studies in humans have better depicted human Th17 cells than studies in mice.

Subsets and Function Changes of Th Cells in the Bone Marrow of Patients with Immune Related Pancytopenia.

Objectives To explore the subsets and function of T helper (Th) in bone marrow of the patients with immune related pancytopenia(IRP). Methods The CD4+ cells producing IFN-γ or IL-4 in cytoplasm were defined as Th1 or Th2 cells respectively. All these cells in bone marrow were measured from 16 normal controls, 25 untreated IRP patients; The mRNA expressions of IL-4, IL-10, IFN-γ and IL-2 genes in unstimulated bone marrow mononuclear cells(BMMNC)from 25 untreated IRP patients, 10 normal controls were measured by reverse transcription polymerase chain reaction (RT-PCR). Results The percentage of Th1 cells, Th2 cells and ratio of Th1/Th2 in bone marrow of normal controls was: 0.42%, 0.24%, 1.57 respectively, and the percentage of Th1 cells in untreated patients with IRP was 0.58%, which was not markedly different from the that of normal controls(t=0.903, P>0.05). But the percentage of Th2 cells of the patients with IRP was significantly higher than that of normal controls(t=4.673, P<0.01), and the balance of Th1/Th2 shifted to Th2 more significantly by comparing to that of normal controls (t=4.880, P<0.01). The mRNA expressions of IL-4 and IL-10 in the Th2 cells of the untreated IRP patients were significantly higher than those of the normal controls, however difference of the expressions of IFN-γ and IL-2 in the Th1 cells were not significantly. Conclusions The percentage of Th2 cells increased in the patients with IRP, and the balance of Th1/Th2 shifted to Th2. And the expression of Th2 type cytokines was more frequent in IRP. The imbalance of subtypes of Th lymphocytes and hyperfunction of Th2 lymphocytes might play important roles in the pathogenic mechanism of IRP, which lead to more B lymphocytes and producing autoantibodies consistenly.