title: Immature thymocytes isolated using a sialic acid-specific lectin are unresponsive to concanavalin A.
abstract: Mouse thymocytes, which are approximately 90% immature cortical cells, are low in surface sialic acid when compared with more mature cortisone-resistant, presumably medullary, thymocytes and peripheral T lymphocytes. Thus, medullary thymocytes bind and are agglutinated by the N-acetylneuraminic acid-specific lectin, lobster agglutinin 1 (LAgl), whereas cortical thymocytes are not agglutinated by this lectin. It is demonstrated herein that mouse cortical thymocytes, purified using LAgl, do not respond to the mitogenic effects of concanavalin A (Con A). The lack of response to this lectin is not due to depletion of macrophages, since addition of macrophages does not restore the response. Populations of LAgl-negative thymocytes can be made to respond weakly to Con A by the addition of interleukin 2, but this response appears to be due to the presence of a few contaminating LAg1-binding thymocytes since it is abolished by treatment of the cells with rabbit anti-LAgl serum plus complement. Therefore highly purified cortical thymocytes not only cannot respond to Con A, but also they cannot be induced to respond by the addition of the T cell growth factor, interleukin 2. Thymocytes isolated by a single criterion, that is by virtue of their low amount of surface sialic acid, appear to be a truly immature population of thymocytes.
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002469:Cell Separation; D003208:Concanavalin A / Q000494:pharmacology*; D005260:Female; D007376:Interleukin-2 / Q000494:pharmacology; D037102:Lectins / Q000494:pharmacology*; D008213:Lymphocyte Activation; D008264:Macrophages / Q000276:immunology; D008297:Male; D051379:Mice; D008121:Nephropidae; D011817:Rabbits; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*
chemical_list: D007376:Interleukin-2; D037102:Lectins; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; D003208:Concanavalin A