Cell migration is crucial for thymocyte differentiation, and the cellular interactions involved now begin to be unraveled, with chemokines, extracellular matrix (ECM) proteins, and their corresponding receptors being relevant in such oriented movement of thymocytes. This notion derives from in vitro, ex vivo, and in vivo experimental data, including those obtained in genetically engineered and spontaneous mutant mice. Thymic microenvironmental cells produce both groups of molecules, whereas developing thymocytes express chemokine and ECM receptors. It is important that although chemokines and ECM proteins can drive thymocyte migration per se, a combined role of these molecules likely concurs for the resulting migration patterns of thymocytes in their various differentiation stages. In this respect, among ECM moieties, there are proteins with opposing functions, such as laminin or fibronectin versus galectin-3, which promote, respectively, adhesion and de-adhesion of thymocytes to the thymic microenvironment. How chemokines and ECM are produced and degraded remains to be more clearly defined. Nevertheless, matrix metalloproteinases (MMPs) likely play a role in the intrathymic ECM breakdown. It is interesting that these molecules also degrade chemokines. Thus, the physiological migration of thymocytes should be conceived as a resulting vector of multiple, simultaneous, or sequential stimuli, involving chemokines, adhesive, and de-adhesive ECM proteins. Moreover, these interactions may be physiologically regulated in situ by matrix MMPs and are influenced by hormones. Accordingly, one can predict that pathological changes in any of these loops may result in abnormal thymocyte migration. This actually occurs in the murine infection by the protozoan Trypanosoma cruzi, the causative agent of Chagas disease. In this model, the abnormal release of immature thymocytes to peripheral lymphoid organs is correlated with the higher migratory response to ECM and chemokines. Lastly, the fine dissection of the mechanisms governing thymocyte migration will provide new clues for designing therapeutic strategies targeting developing T cells. The most important function of the thymus is to generate T lymphocytes, which once leaving the organ, are able to colonize specific regions of peripheral lymphoid organs, the T cell zones, where they can mount and regulate cell-mediated, immune responses. This intrathymic T cell differentiation is a complex sequence of biological events, comprising cell proliferation, differential membrane protein expression, gene rearrangements, massive programmed cell death, and cell migration. In this review, we will focus on the mechanisms involved in controlling the migration of thymocytes, from the entrance of cell precursors into the organ to the exit of mature T cells toward peripheral lymphoid organs. Nevertheless, to better comprehend this issue, it appeared worthwhile to briefly comment on some key aspects of thymocyte differentiation and the tissue context in which it takes place, the thymic microenv...

No abstract

Pulmonary tuberculosis (PTB) is associated with chronic inflammation and anemia. How anemia impacts systemic inflammation in PTB patients undergoing antitubercular therapy (ATT) is not fully understood. In the present study, data on several blood biochemical parameters were retrospectively analyzed from 118 PTB patients during the first 60 days of ATT. Multidimensional statistical analyses were employed to perform detailed inflammatory profiling of patients stratified by anemia status prior to treatment. Anemia was defined as hemoglobin levels <12.5 g/dL for female and <13.5 g/dL for male individuals. The findings revealed that most of anemia cases were likely caused by chronic inflammation. A distinct biosignature related to anemia was detected, defined by increased values of uric acid, C-reactive protein, and erythrocyte sedimentation rate. Importantly, anemic patients sustained increased levels of several biochemical markers at day 60 of therapy. Preliminary analysis failed to demonstrate association between persistent inflammation during ATT with frequency of positive sputum cultures at day 60. Thus, TB patients with anemia exhibit a distinct inflammatory profile, which is only partially reverted at day 60 of ATT.

During acute infection with Trypanosoma cruzi, the causative agent of Chagas' disease, the thymus undergoes intense atrophy followed by a premature escape of CD4 ؉ CD8 ؉ immature cortical thymocytes. Here we report a pivotal role for the endogenous lectin galectin-3 in accelerating death of thymocytes and migration of these cells away from the thymus after T. cruzi infection. We observed a pronounced increase in galectin-3 expression that paralleled the extensive depletion of CD4 ؉ CD8 ؉ immature thymocytes after infection. In vitro, recombinant galectin-3 induced increased levels of death in cortical immature thymocytes. Consistent with the role of galectin-3 in promoting cell death, thymuses from gal-3 ؊/؊ mice did not show cortical thymocyte depletion after parasite infection in vivo. In addition, galectin-3 accelerated laminin-driven CD4 ؉ CD8 ؉ thymocyte migration in vitro and in vivo induced exportation of CD4 ؉ CD8 ؉ cells from the thymus to the peripheral compartment. Our findings provide evidence of a novel role for galectin-3 in the regulation of thymus physiology and identify a potential mechanism based on proteinglycan interactions in thymic atrophy associated with acute T. cruzi infection.

The process of thymocyte differentiation occurs within the context of the thymic microenvironment, in which T cell precursors interact with thymic microenvironmental cells and extracellular matrix. Here we studied the expression of galectin‐3, a β‐galactoside binding lectin, in the thymus of young adult mice. Galectin‐3 was found mainly in the medulla and to a lesser extent in the cortex. We further showed that distinct microenvironmental elements, such as thymic epithelial cells, the epithelial component of thymic nurse complexes and phagocytic cells of the thymic reticulum produce, secrete and accumulate galectin‐3 on the cell surface. Functionally, galectin‐3‐enriched medium inhibited in vitro thymocyte interactions with thymic microenvironmental cells, accelerated the release of thymocytes from thymic nurse cells and inhibited the reconstitution of these lymphoepithelial complexes. These effects were blocked by exogenous lactose (Galβ1–4Glc), but not melibiose (Galα1–6Glc), and by a monospecific anti‐galectin‐3 antibody. Recombinant galectin‐3 also inhibited thymocyte/thymic epithelial cell interactions. Our data indicate that intrathymically produced galectin‐3 disrupts thymocyte/microenvironmental cell interactions, thus acting as a de‐adhesion molecule.

BackgroundClinical trials that evaluate new anti-tubercular drugs and treatment regimens take years to complete due to the slow clearance of Mycobacterium tuberculosis infection and the lack of early biomarkers that predict treatment outcomes. Host Inflammation markers have been associated with tuberculosis (TB) pathogenesis. In the present study, we tested if circulating levels of C-reactive protein (CRP) and ferritin reflect mycobacterial loads and inflammation in pulmonary TB (PTB) patients undergoing anti-tuberculous therapy (ATT).MethodsProspective measurements of CRP and ferritin, used as readouts of systemic inflammation, were performed in cryopreserved serum samples from 165 Brazilian patients with active PTB initiating ATT. Associations between levels of these laboratory parameters with mycobacterial loads in sputum as well as with sputum conversion at day 60 of ATT were tested.ResultsCirculating levels of both ferritin and CRP gradually decreased over time on ATT. At pre-treatment, concentrations of these parameters were unable to distinguish patients with positive from those with negative acid-fast bacilli (AFB) in sputum cultures. However, patients who remained with positive cultures at day 60 of ATT exhibited heightened levels of these inflammatory markers compared to those with negative cultures at that time point.ConclusionsCRP and Ferritin levels in serum may be useful to identify patients with positive cultures at day 60 of ATT.

Background: Mycobacterium tuberculosis infection is known to cause inflammation and lung tissue damage in high-risk populations. Nevertheless, direct associations between mycobacterial loads, systemic inflammation and pulmonary lesions upon treatment initiation have not been fully characterized. In the present exploratory study, we prospectively depict the immune profile, microbial clearance and evolution of radiographic lesions in a pulmonary tuberculosis (PTB) patient cohort before and 60 days after anti-tuberculous treatment (ATT) initiation. Methods: Circulating levels of cytokines (IL-2, IL-4, IL-6, IL-10, IFN-γ, TNF-α) and C-reactive protein (CRP), as well as values of erythrocyte sedimentation rate (ESR) were measured in cryopreserved serum samples obtained from 73 PTB patients at pre-ATT and day 60 of treatment. Changes of the immune profile over time were compared with mycobacterial loads in sputum and culture conversion at day 60 of ATT. Additional analyses tested associations between improvement of chest radiographic lesions at day 60 and pre-treatment status of inflammation and mycobacterial loads.

Background: Pulmonary tuberculosis (PTB) can lead to lung tissue damage (LTD) and compromise the pulmonary capacity of TB patients that evolve to severe PTB. The molecular mechanisms involved in LTD during anti-tuberculous treatment (ATT) remain poorly understood.Methods and findings: We evaluated the role of neutrophil extracellular trap (NET) and the occurrence of LTD through chest radiographic images, the microbial load in sputum, and inflammatory serum profile (IL-12p40/p70, IL-8, IL-17A, IL-23, VEGF-A, MMP-1, and -8, galectin-3, citrunillated histone H3—cit-H3, alpha-1-antitrypsin—α1AT, C-reactive protein—CRP and albumin) in a cohort of 82 PTB patients before and after 60 days of ATT. Using univariate analysis, LTD was associated with neutrophilia and increase of several inflammatory proteins involved in the neutrophil-mediated response, being cit-H3 the more related to the event. In the multivariate analysis, neutrophilia and cit-H3 appear as directly related to LTD. The analysis of the ROC curve at day 60 presented AUC of 0.97 (95.0% CI 0.95–1). Interestingly, at day 0 of ATT, these biomarkers demonstrated fine relation with LTD showing an AUC 0.92 (95.0% CI 0.86–0.99). Despite of that, the same molecules have no impact in culture conversion during ATT.Conclusions: Our data revealed that NETs may play a key role in the pathway responsible for non-specific inflammation and tissue destruction in PTB. High level of cit-H3 and low level of α1AT was observed in the serum of severe TB patients, suggesting a breakdown in the intrinsic control of NET-driven tissue damage. These data show a new insight to knowledge TB immunopathogenesis, the role of neutrophil and NET pathway. Likewise, we identified possible biomarkers to screening of PTB patients eligible to adjuvants therapies, as anti-inflammatories and alpha-1-antitrypsin.