Search for thymocyte growth-stimulating activity in extracts of different tissues and among established growth factors and thymic maturation hormones.
A thymocyte specific growth factor has previously been prepared from calf thymus. Similar activity is now shown to be present in thymus and spleen of guinea pigs, but not in lymph nodes, liver and kidney. Purified thymic maturation hormones, interleukins and several growth factors for other cell types than lymphocytes were tested and found not to stimulate DNA synthesis of thymocytes. A slight activity was found in thymosin fraction 5, known to contain at least 35 polypeptides. Our factor lacked comitogenic effect when tested in combination with concanavalin A (Con A) and phytohemagglutinin, did not promote continuous growth of ConA-induced lymphoblasts and did not affect the cyclic AMP level of thymocytes. The data indicate that our factor is functionally distinct from the purified hormones and defined factors tested.
D000818:Animals; D002454:Cell Differentiation; D003208:Concanavalin A / Q000494:pharmacology; D006133:Growth Substances / Q000302:isolation & purification*; D006168:Guinea Pigs; D007376:Interleukin-2 / Q000032:analysis; D008934:Mitogens / Q000276:immunology; D010835:Phytohemagglutinins / Q000494:pharmacology; D013951:Thymus Hormones / Q000032:analysis
D006133:Growth Substances; D007376:Interleukin-2; D008934:Mitogens; D010835:Phytohemagglutinins; D013951:Thymus Hormones; D003208:Concanavalin A