       Document 0520
 DOCN  M9620520
 TI    Positive selection of thymocytes involves sustained interactions with
       the thymic microenvironment.
 DT    9602
 AU    Wilkinson RW; Anderson G; Owen JJ; Jenkinson EJ; Department of
       Anatomy/Center for Clinical Research in Immunology; and Signaling,
       Medical School, University of Birmingham, United; Kingdom.
 SO    J Immunol. 1995 Dec 1;155(11):5234-40. Unique Identifier : AIDSLINE
       MED/96072798
 AB    CD4+8+ cortical thymocytes are critically dependent upon interaction
       with the thymic epithelium to undergo positive selection and maturation
       into single-positive CD4+ or CD8+ cells. Here we investigate further the
       nature of this interaction and provide evidence that positive selection
       requires sustained, rather than single hit, interaction with thymic
       stromal cells. We also show that calcineurin-mediated signaling in
       thymocytes is required for the initial stages of positive selection, but
       is not essential throughout the period of thymocyte dependence on
       stromal cell contact during positive selection. In addition, we show
       that double-positive thymocytes that have initiated positive selection
       (CD69+4+8+) and newly generated single-positive (CD69+4+) cells differ
       markedly in response to the same stimulus through the TCR. The former
       undergo deletion, whereas the latter proliferate, indicating that a
       critical change in response to TCR ligation occurs within the narrow
       developmental window between these two stages.
 DE    Animal  Antigens, CD/IMMUNOLOGY  Antigens, Differentiation,
       T-Lymphocyte/IMMUNOLOGY  Cell Differentiation/PHYSIOLOGY  Clonal
       Deletion  CD4-Positive T-Lymphocytes/*CYTOLOGY/IMMUNOLOGY  CD8-Positive
       T-Lymphocytes/*CYTOLOGY/IMMUNOLOGY  Epithelium/PHYSIOLOGY  Mice  Mice,
       Inbred BALB C  Stromal Cells/PHYSIOLOGY  Superantigens/IMMUNOLOGY
       Support, Non-U.S. Gov't  Thymus Gland/*CYTOLOGY/EMBRYOLOGY/GROWTH &
       DEVELOPMENT/IMMUNOLOGY  JOURNAL ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).

