Epithelial Cell-Specific Laminin 5 Is Required for Survival of Early Thymocytes

Abstract

The gene LamC2 encoding the γ2 chain of laminin 5, an epithelial cell-specific extracellular matrix protein, was identified in a PCR-based subtracted cDNA library from mouse thymic stromal cells. The mRNA existed in two alternative forms (5.1 and 2.4 kb). The full-length message was highly expressed in SCID thymus and in a nurse cell line, but not in other thymic epithelial cell lines, while the short form was more widely expressed. In situ hybridization and immunohistochemical staining revealed laminin 5 expression mostly in the subcapsular region of the adult thymus. Addition to fetal thymic organ cultures of a cell adhesion-blocking mAb to the α3 chain of laminin 5 interrupted T cell development. There was a 40% reduction in the total yield of thymocytes, and the most profound decrease (75–90%) was seen in the CD25+CD44+ and CD25+CD44−subsets of the CD4−CD8− double negative fraction. Most of the surviving double negative thymocytes expressed Sca-1, and there were significant increases in the number of cells with CD69 expression and in the fraction of annexin V-stained cells. None of these changes were observed with a nonblocking anti-laminin α3 chain mAb. These results suggest that the interaction between double negative thymoctyes and laminin 5 made by subcapsular epithelial cells is required for the survival and differentiation of mouse thymocytes.

Stromal Cells Provide the Matrix for Migration of Early Lymphoid Progenitors Through the Thymic Cortex

“…Although static adhesion does not allow measurement of absolute affinity for a given ligand, it can be used to determine relative affinity of cells expressing a given set of receptors. Adhesion to LN5 was not tested, because it is found only in the basal layers of the thymic capsule and thymic blood vessels (28,29), neither of which are primary sites for DN localization in the cortex (19). For the remaining ECM ligands, namely FN and LN1, 96-well tissue culture trays were coated with optimal levels of purified ECM proteins (see Materials and Methods), and equal numbers of cells at each stage were added.…”

Characterization of a conduit system containing laminin-5 in the human thymus: a potential transport system for small molecules

“…Rather, a network of interconnected TECs that permeates the cortex and the medulla of the thymic lobules has been suggested to provide a matrix for the migration of thymocytes (Ushiki, 1986;Prockop et al, 2002;Petri, 2003). Important constituents of the ECM of the thymus belong to the laminin family of basement membrane molecules (Kim et al, 2000;Magner et al, 2000;Geberhiwot et al, 2001;Kutlesa et al, 2002a). Laminins are heterotrimeric molecules consisting of ␣, ␤ and ␥ chains.…”

Early intra-amniotic gene transfer using lentiviral vector improves skin blistering phenotype in a murine model of Herlitz junctional epidermolysis bullosa

“…Newborns with HJEB have major involvement of the airways, gastrointestinal and vesicourinary tracts and possibly abnormalities of T-cell development resulting in immune deficiency. 28 In the murine setting, this may have resulted in poor feeding, maternal neglect, hypoproteinemia, electrolyte abnormalities, sepsis and early demise. In the context of potential clinical application, it is important to emphasize that even full correction of the skin phenotype alone may not result in complete correction of manifestations of the disease.…”