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Åke Lernmark

Principal investigator

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Low-density cells isolated from the rat thymus resemble branched cortical macrophages and have a reduced capability of rescuing double-positive thymocytes from apoptosis in the BB-DP rat.


  • V Sommandas
  • EA Rutledge
  • B Van Yserloo
  • J Fuller
  • Åke Lernmark
  • HA Drexhage

Summary, in English

Biobreeding-diabetes prone (BB-DP) rats spontaneously develop organ-specific autoimmunity and are severely lymphopenic and particularly deficient in ART2+ regulatory T cells. A special breed, the so-called BB-diabetic-resistant (DR) rats, are not lymphopenic and do not develop organ-specific autoimmunity. The genetic difference between both strains is the lymphopenia (lyp) gene. Intrathymic tolerance mechanisms are important to prevent autoimmunity, and next to thymus epithelial cells, thymus APC play a prominent part in this tolerance. We here embarked on a study to detect defects in thymus APC of the BB-DP rat and isolated thymus APC using a protocol based on the low-density and nonadherent character of the cells. We used BB-DP, BB-DR, wild-type F344, and F344 rats congenic for the lyp gene-containing region. The isolated thymus, nonadherent, low-density cells appeared to be predominantly ED2+ branched cortical macrophages and not OX62+ thymus medullary and cortico-medullary dendritic cells. Functionally, these ED2+ macrophages were excellent stimulators of T cell proliferation, but it is more important that they rescued double-positive thymocytes from apoptosis. The isolated thymus ED2+ macrophages of the BB-DP and the F344.lyp/lyp rat exhibited a reduced T cell stimulatory capacity as compared with such cells of nonlymphopenic rats. They had a strongly diminished capability of rescuing thymocytes from apoptosis (also of ART2+ T cells) and showed a reduced Ian5 expression (as lyp/lyp thymocytes do). Our experiments strongly suggest that branched cortical macrophages play a role in positive selection of T cells in the thymus and point to defects in these cells in BB-DP rats.


  • Diabetes and Celiac Unit

Publishing year







Journal of Leukocyte Biology





Document type

Journal article


John Wiley and Sons


  • Endocrinology and Diabetes



Research group

  • Diabetes and Celiac Unit


  • ISSN: 0741-5400