Influência in vitro do fator-1 de crescimento semelhante a insulina sobre as moléculas envolvidas na diferenciação de Linfócitos T

Abstract

Insulin-like growth factor-1 (IGF-1), in addition to its classic effects on cell proliferation and organism growth, has pleiotropic actions on the immune system, particularly on the thymus. In order to contribute to this knowledge, the objective was to evaluate the influence of IGF-1 on molecules involved in the differentiation of T lymphocytes in vitro. For the study, a co-culture with thymic stromal cells (CETc) and thymocytes, from the time of C57BL/6 mice, aged 4 to 6 weeks of both sexes. Initially, the cell types obtained from thymic stroma were demonstrated, which were identified mainly as cortical and medullary epithelial cells, as well as macrophages, dendritic cells and fibroblasts. The expression of MHC-I and MHC-II was observed on the surface of the cells, as well as the expression of the integrins VLA-4, VLA-5 and VLA-6. In the co-culture model, the viability of the thymocytes was evaluated and 71% of the thymocytes were found to be viable. Treatment with IGF-1 decreased MHC-I and VLA-6 expression on the CETC surface after co-culture with the thymocytes. However, MHC-II and VLA-5 expression increased on the cell surface as compared to the control. In addition, IGF-1 has been shown to be capable of enhancing a fibronectin deposition by CETc when co-cultured with thymocytes. However, a laminin deposition was decreased in CETc in the presence of IGF-1. Concerning IL-7 (IL-7R) receptor expression in thymocytes, treatment with IGF-1 increased expression of this receptor in the total population and in the CD4+CD8- single-positive subpopulation. However, this treatment reduced IL-7R expression in the CD4+CD8+ and CD4-CD8+ subpopulations. We evaluated the percent number of thymocyte subpopulations after co-cultivation with CETc, it was found that IGF-1 was able to increase the percentage of thymocytes from CD4+ CD8- single-positive subpopulation. Finally, IGF-1 treatment increased a 57.3% Zbtb7b gene expression, involved in the differentiation of CD4+CD8+ thymocytes and decreased 23.5% Runx1 gene expression, involved in differentiation of CD4-CD8+ thymocytes. Together, the data obtained int this study demonstrate the participation of IGF-1 in the thymocyte / thymic stroma interactions, especially in the in vitro differentiation of thymocytes in CD4SP T lymphocytes, via ThPOK transcription factor.