LIMITING DILUTION ANALYSIS OF ALLOANTIGEN-REACTIVE LYMPHOCYTES-T .2. EFFECT OF CORTISONE AND CYCLOPHOSPHAMIDE ON CYTOLYTIC LYMPHOCYTES-T PRECURSOR FREQUENCIES IN THE THYMUS

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 1  (1-2) , 119-131
Abstract
A minimal estimate of the frequency of cytolytic T [thymus-derived] lymphocyte precursors (CTL-P) in the thymus was determined by application of Poisson statistics to limiting dilution analysis. A mean CTL-P frequency of 1/1467 was obtained for C57BL/6 (H-2b) thymus cells activated by DBA/2 (H-2d) irradiated spleen cells and assayed against P-815 mastocytoma (H-2d) target cells. CTL-P frequencies were also obtained for spleen, nylon wool column purified spleen, peripheral blood and lymph node cell populations. The effect of in vivo drug treatments on CTL-P frequencies was then examined. Cortisone at 100 mg/kg dramatically increased the CTL-P frequency in thymus by more than 20-fold despite a drastic reduction in the number of total thymus cells. The same cortisone treatment did not affect the CTL-P frequency in spleen. In contrast, cyclophosphamide at 300 mg/kg decreased the CTL-P frequency in spleen by more than 10-fold without affecting that in thymus. Cyclophosphamide at 100 mg/kg did not produce any significant change. A detailed explanation of the calculation of CTL-P frequencies was provided and their validity was discussed.