DIFFERENTIATION OF LYMPHOCYTES-T .5. EVIDENCE FOR INTRA-THYMIC DEATH OF MOST THYMOCYTES

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 1  (3) , 151-162
Abstract
The DNA of CBA mouse thymocytes was simultaneously labeled with the efficiently reutilized precursor [3H]TdR [thymidine] and the poorly reutilized precursor [125I]UdR [uridine] and the subsequent rate of loss of the 2 thymidine analogs was used to compute the extent of local thymidine reutilization. This should provide a minimum estimate of thymocyte death within the thymus. In agreement with published data, reutilization of thymidine in the steady state adult mouse thymus was about 61%. Adrenalectomy showed that this turnover was not due to steroid-mediated stress effects, nor could it be attributed to direct effects of [125I]UdR itself. Most of the initial uptake and the subsequent turnover was within the major high .theta. thymus subpopulation. A similar study with the growing thymus of 7 day old mice, when the demand for T cells in the periphery should be high, also revealed a high level (63%) of thymidine reutilization. A minimum of 60% of newly formed thymocytes apparently die within the thymus, and this is apparently a constant and normal aspect of thymus function. This would be compatible with some form of negative selection for the appropriate developing T cells.