Digital NFATc2 Activation per Cell Transforms Graded T Cell Receptor Activation into an All-or-None IL-2 Expression

The expression of interleukin-2 (IL-2) is a key event in T helper (Th) lymphocyte activation, controlling both, the expansion and differentiation of effector Th cells as well as the activation of regulatory T cells. We demonstrate that the strength of TCR stimulation is translated into the frequency of memory Th cells expressing IL-2 but not into the amount of IL-2 per cell. This molecular switch decision for IL-2 expression per cell is located downstream of the cytosolic Ca2+ level. Here we show that in a single activated Th cell, NFATc2 activation is digital but NF-κB activation is graded after graded T cell receptor (TCR) signaling. Subsequently, NFATc2 translocates into the nucleus in an all-or-none fashion per cell, transforming the strength of TCR-stimulation into the number of nuclei positive for NFATc2 and IL-2 transcription. Thus, the described NFATc2 switch regulates the number of Th cells actively participating in an immune response

Trypanosoma cruzi Disrupts Thymic Homeostasis by Altering Intrathymic and Systemic Stress-Related Endocrine Circuitries

Submitted by sandra infurna ([email protected]) on 2016-01-28T11:09:52Z No. of bitstreams: 1 vinicius_carvalho_etal_IOC_2013.pdf: 3865097 bytes, checksum: 65caa965de5487006a9dcafcdb9e2293 (MD5)Approved for entry into archive by sandra infurna ([email protected]) on 2016-01-28T11:22:36Z (GMT) No. of bitstreams: 1 vinicius_carvalho_etal_IOC_2013.pdf: 3865097 bytes, checksum: 65caa965de5487006a9dcafcdb9e2293 (MD5)Made available in DSpace on 2016-01-28T11:22:36Z (GMT). No. of bitstreams: 1 vinicius_carvalho_etal_IOC_2013.pdf: 3865097 bytes, checksum: 65caa965de5487006a9dcafcdb9e2293 (MD5) Previous issue date: 2013Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Pesquisa sobre o Timo. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Inflamação. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Inflamação. Rio de Janeiro, RJ, Brasil.National University of Rosario and CONICET. Faculty of Medical Sciences. Institute of Immunology. Rosario, Argentina.National University of Rosario and CONICET. Faculty of Medical Sciences. Institute of Immunology. Rosario, Argentina.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Pesquisa sobre o Timo. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Pesquisa sobre o Timo. Rio de Janeiro, RJ, Brasil / Universidade Federal do Rio de Janeiro. Instituto de Microbiologia Paulo de Góes. Rio de Janeiro, RJ, Brasil.We have previously shown that experimental infection caused by Trypanosoma cruzi is associated with changes in the hypothalamus-pituitary-adrenal axis. Increased glucocorticoid (GC) levels are believed to be protective against the effects of acute stress during infection but result in depletion of CD4+ CD8+ thymocytes by apoptosis, driving to thymic atrophy. However, very few data are available concerning prolactin (PRL), another stress-related hormone, which seems to be decreased during T. cruzi infection. Considering the immunomodulatory role of PRL upon the effects caused by GC, we investigated if intrathymic cross-talk between GC and PRL receptors (GR and PRLR, respectively) might influence T. cruziinduced thymic atrophy. Using an acute experimental model, we observed changes in GR/PRLR cross-activation related with the survival of CD4+ CD8+ thymocytes during infection. These alterations were closely related with systemic changes, characterized by a stress hormone imbalance, with progressive GC augmentation simultaneously to PRL reduction. The intrathymic hormone circuitry exhibited an inverse modulation that seemed to counteract the GC-related systemic deleterious effects. During infection, adrenalectomy protected the thymus from the increase in apoptosis ratio without changing PRL levels, whereas an additional inhibition of circulating PRL accelerated the thymic atrophy and led to an increase in corticosterone systemic levels. These results demonstrate that the PRL impairment during infection is not caused by the increase of corticosterone levels, but the opposite seems to occur. Accordingly, metoclopramide (MET)-induced enhancement of PRL secretion protected thymic atrophy in acutely infected animals as well as the abnormal export of immature and potentially autoreactive CD4+ CD8+ thymocytes to the periphery. In conclusion, our findings clearly show that Trypanosoma cruzi subverts mouse thymus homeostasis by altering intrathymic and systemic stress-related endocrine circuitries with major consequences upon the normal process of intrathymic T cell development