title: MHC non-restricted, CD95-independent apoptosis of immature thymocytes induced by thymic epithelial cells.
abstract: The interaction of thymocytes with thymic epithelial cells in the absence of an exogenous antigen was studied in vitro. Thymic, but not splenic epithelial cells induced apoptosis of thymocytes. A thymic epithelial cell line (TEC) induced apoptosis of thymocytes but not of splenic T-cells. The target population for TEC-induced death were immature CD4(+)8(+) (double positive), but not mature single positive thymocytes. TEC also induced DNA fragmentation in day 18 foetal thymocytes, most of which are CD4(+)8(+) cells. Radiation leukemia virus (RadLV)-transformed thymic lymphoma clones expressing various phenotypes reflected this sensitivity, in that a CD4(+)8(+)3(+) clone apoptosed by thymic epithelial cells or TEC. Other, single positive or double negative clones were resistant. Thymocytes from C3H (H-2(k)), C57BL/6 (H-2(b)) and Balb/C (H-2(d)) mice apoptosed equally in response to either C57BL/6 thymic epithelial cells or TEC (H-2(b) x H-2(d)). Likewise, thymocytes from MRLIpr((-/-)) and B6Ipr((-/-)) mice, which do not express CD95 were also apoptosed by TEC.The data suggest that thymic epithelial cells induce MHC non-restricted, Fas-independent apoptosis of immature thymocytes. This response may reflect a mechanism through which thymocytes expressing TcR with no affinity to self MHC/peptide complexes are eliminated.
authors.affiliation: The Lautenberg Center for General and Tumor Immunology, The Hebrew University, Hadassah Medical School, Jerusalem, Israel.
authors.forename: R
authors.initials: R
authors.lastname: Guy
authors.forename: I
authors.initials: I
authors.lastname: Gafanovich
authors.forename: N
authors.initials: N
authors.lastname: Rosenheimer
authors.forename: E
authors.initials: E
authors.lastname: Oron
authors.forename: E
authors.initials: E
authors.lastname: Yefenof
authors.forename: Y
authors.initials: Y
authors.lastname: Zilberman