title: Lymphotoxin pathway and Aire influences on thymic medullary epithelial cells are unconnected.
abstract: The lymphotoxin pathway is critical for the development and maintenance of peripheral lymphoid organs. Mice with deficiencies in members of this pathway lack lymph nodes and Peyer's patches and have abnormal spleen architecture. These animals also develop autoantibodies to and lymphocytic infiltrates of multiple organs, provoking speculation that the lymphotoxin pathway may play a role in central tolerance induction. Indeed, a series of reports has claimed that lymphotoxin signals control the expression of Aire, a transcriptional regulator that is expressed in medullary epithelial cells of the thymus, mediates ectopic transcription of genes encoding a variety of peripheral tissue Ags, and promotes clonal deletion of self-reactive thymocytes. However, one report argued that lymphotoxin signals regulate the composition and organization of the thymus, particularly of the medullary epithelial compartment. Herein, we resolve this controversy in favor of the latter view. The expression and function of Aire were unaffected in medullary epithelial cells of mice lacking either lymphotoxin beta receptor or the lymphotoxin alpha-chain, and there was minimal overlap between the sets of genes controlled by Aire and lymphotoxin. Instead, both knockout lines showed abnormal medullary epithelial cell organization, and the line lacking the beta receptor had significantly fewer medullary epithelial cells. In short, the lymphotoxin pathway drives the developmental rather than selectional properties of thymic stromal cells.
authors.affiliation: Department of Medicine, Section on Immunology and Immunogenetics, Joslin Diabetes Center, Brigham and Women's Hospital, Boston, MA 02215, USA.
authors.forename: Emily S
authors.initials: ES
authors.lastname: Venanzi
authors.forename: Daniel H D
authors.initials: DH
authors.lastname: Gray
authors.forename: Christophe
authors.initials: C
authors.lastname: Benoist
authors.forename: Diane
authors.initials: D
authors.lastname: Mathis
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D004847:Epithelial Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D053259:Lymphotoxin beta Receptor / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D008233:Lymphotoxin-alpha / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D015398:Signal Transduction / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000096927:AIRE Protein
chemical_list: D053259:Lymphotoxin beta Receptor; D008233:Lymphotoxin-alpha; D014157:Transcription Factors; D000096927:AIRE Protein