EXTRACELLULAR-MATRIX COMPONENTS OF THE MOUSE THYMUS MICROENVIRONMENT .4. MODULATION OF THYMIC NURSE CELLS BY EXTRACELLULAR-MATRIX LIGANDS AND RECEPTORS

Extracellular matrix (ECM) proteins can influence cell migration and d ifferentiation in a variety of cell systems. Within the thymus, these molecules are heterogeneously distributed, and their physiological rol e 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 fro m TNC, whereas anti-ECM antibodies exhibited a blocking effect. Simila r results were obtained with anti-ECM receptor reagents. Moreover, the se antibodies abrogated in vitro reconstitution of TNC complexes and t hymocyte adhesion to TNC-derived epithelial cultures. Our results indi cate that lymphocyte traffic in TNC (comprising both entrance into aci d exit from the epithelial structure) is affected by interactions invo lving 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.