title: STOP! In the name of positive selection.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Cahalan
mesh_terms: D020013:Calcium Signaling; D002454:Cell Differentiation; D002465:Cell Movement; D017154:Stromal Cells / Q000166:cytology / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism