title: Why positive selection?
authors.affiliation: Laboratory of Molecular and Cellular Immunology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, MD 20892.
authors.forename: P
authors.initials: P
authors.lastname: Matzinger
mesh_terms: D000818:Animals; D015704:CD4 Antigens; D016827:CD8 Antigens; D006801:Humans; D008285:Major Histocompatibility Complex / Q000502:physiology*; D008954:Models, Biological; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D013601:T-Lymphocytes / Q000502:physiology*; D013950:Thymus Gland / Q000166:cytology
chemical_list: D015704:CD4 Antigens; D016827:CD8 Antigens; D011948:Receptors, Antigen, T-Cell