       Document 0404
 DOCN  M9610404
 TI    Intermediate steps in thymic positive selection. Generation of CD4-8+ T
       cells in culture from CD4+8+, CD4int8+, and CD4+8int thymocytes with
       up-regulated levels of TCR-CD3.
 DT    9601
 AU    Kydd R; Lundberg K; Vremec D; Harris AW; Shortman K; Walter and Eliza
       Hall Institute of Medical Research, Melbourne,; Victoria, Australia.
 SO    J Immunol. 1995 Oct 15;155(8):3806-14. Unique Identifier : AIDSLINE
       MED/96003419
 AB    Minor thymus subpopulations representing possible intermediates in
       thymic positive selection were isolated by cell sorting from bcl-2
       transgenic mice, and cultured 1 to 4 days in simple medium to assess
       their ability to spontaneously develop the surface phenotype of mature T
       cells. Recovery of cells was in the 60 to 80% range, and no cell
       proliferation occurred. Only cells originally expressing high, near
       mature T cell levels of CD3 developed further in culture by
       down-regulation of CD4 or CD8. The main mature cell product was CD4-8+,
       regardless of whether the starting phenotype of the CD3high
       intermediates was CD4+8+, CD4int8+, or CD4+8int; only an intermediate
       subpopulation expressing the highest levels of CD4 (CD4high8int)
       produced a dominance of CD4+8- mature progeny. Partial down-regulation
       of CD8 was therefore not a good indicator of CD4+ T lineage commitment.
       These and previous results indicate that maturation to the CD8+ T
       lineage involves a rapid up-regulation of the TCR-CD3 complex, but a
       relatively slow down-regulation of CD4; it may also involve a partial,
       transient reduction in surface CD8. In contrast, maturation to the CD4+
       T lineage involves a relatively rapid down-regulation of CD8, with
       maintenance of high levels of CD4. There appears to be a marked
       asymmetry in the developmental steps leading from CD4+8+ thymocytes to
       the CD8+ or to the CD4+ T cell lineage.
 DE    Animal  Cell Differentiation  CD4-CD8 Ratio  CD4-Positive
       T-Lymphocytes/*IMMUNOLOGY  CD8-Positive T-Lymphocytes/*IMMUNOLOGY
       Lymphocyte Transformation  Mice  Mice, Inbred C57BL  Mice, Transgenic
       Proto-Oncogene Proteins/GENETICS  Receptor-CD3 Complex, Antigen,
       T-Cell/*METABOLISM  Support, Non-U.S. Gov't  T-Lymphocyte
       Subsets/*IMMUNOLOGY  Thymus Gland/CYTOLOGY  Up-Regulation
       (Physiology)/*IMMUNOLOGY  JOURNAL ARTICLE

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

