Extracellular matrix components of the mouse thymus microenvironment. IV. Modulation of thymic nurse cells by extracellular matrix ligands and receptors

Abstract

Extracellular matrix (ECM) proteins can influence cell migration and differentiation in a variety of cell systems. Within the thymus, these molecules are heterogeneously distributed, and their physiological role is poorly understood. This prompted us to carry out in vitro studies using the thymic nurse cell (TNC) model. We observed that fibronectin and laminin accelerate spontaneous in vitro release of thymocytes from TNC, whereas anti-ECM antibodies exhibited a blocking effect. Similar results were obtained with anti-ECM receptor reagents. Moreover, these antibodies abrogated in vitro reconstitution of TNC complexes and thymocyte adhesion to TNC-derived epithelial cultures. Our results indicate that lymphocyte traffic in TNC (comprising both entrance into and exit from the epithelial structure) is affected by interactions involving extracellular matrix ligands and receptors. In this respect, the dynamic analysis of thymic nurse cell complexes should be regarded as a relevant in vitro tool for functional studies of distinct adhesion molecules in intrathymic lymphocyte traffic.

Impaired migration of NOD mouse thymocytes: a fibronectin receptor‐related defect

“…Thus, the above experiments tell us that the transit of immature thymocytes through TNC is diminished in NOD mice, and that such a defect is related to the abnormally low VLA-5 expression. It is noteworthy that blocking experiments with anti-VLA-4 plus anti-VLA-5 mAb did not result in complete abrogation of thymocyte adhesion, which is in keeping with the role also played by laminin-mediated interactions in this event [37,38].…”

“…Thus, a functional deficiency of immature thymocytes correlates with the lower VLA-5 expression. As stated below, data related to all adhesion assays were presented as individual values due to variations in the adhesion degree, from experiment to experiment, as previously reported [37,38]. Yet, the results displayed in the panels are representative of at least three similar experiments.…”

“…Actually, some authors claim that TNC harbor CD4 -CD8 -and CD4 + CD8 + cells [35], whereas others sustain that typical TNC contain DP thymocytes [36]. In any case, since entrance and exit of thymocytes in TNC are dependent on ECM-mediated interactions, we considered TNC as an in vitro model for assessing thymocyte migration within the TEC context [34,[37][38]. We observed that TNC-derived epithelial cells from NOD mice produce ECM ligands, including fibronectin and laminin (not shown), and have no decrease in VLA-5 expression, compared to controls (Fig.…”

“…In culture, TNC gradually release thymocytes, an active process that can be semi-quantitatively evaluated [37]. Differential counting of thymocyte-containing TNC versus lymphocyte-free TNC was performed.…”

Identification, structural characterization, and tissue distribution of Tsg-5: a new TNF-stimulated gene

“…57 In order to avoid nonspecific staining, specimens were first incubated with 10 mg/ml normal mouse Ig diluted in 1% BSA/PBS for 30 min. Specific staining with appropriate dilutions (1 : 100) of the anti-Tsg-5 antibodies was carried out for 1 h. Specimens were then washed three times in PBS and subjected to the respective peroxidase-conjugated second antibody (Amersham, Buckinghamshire, UK) for 1 h. For negative controls, we substitute specific antibodies by preimmune sera, applied at the same concentration.…”