Abstract
Five transmissible strains of lymphomatosis were studied. Two strains can be successfully transmitted to any stocks of mice, 3 to related mice only. Mice of stocks yielding from 50 to 100% success upon inoculation with malignant lymphocytes will be designated as susceptible, mice of a stock to which lymphomatosis could not be transmitted will be designated as resistant.
A single exposure of mice to X-rays will increase the susceptibility of the animals to transmissible lymphomatosis. The smallest quantity of X-rays that made resistant mice susceptible to lymphomatosis was about 30 r-units but this amount was effective in only 2 of 13 irradiated mice. The success of inoculations is greater after exposure to larger quantities of X-rays and is about 100% after exposure to sublethal doses (400 to 600 r). The duration of susceptibility is likewise proportional to the quantity of irradiation. About one-third of the mice exposed to sublethal doses of X-rays remained susceptible for 2 or 3 months, but more than one-half of them regained resistance in from 1 to 2 months after irradiation.
A single exposure to sublethal doses of X-rays almost completely destroys the leucocytes of the blood and blood-forming organs but it does not prevent the progressive growth of malignant lymphocytes introduced before such an irradiation into the circulation of healthy mice. The inoculated mice often die of lymphomatosis before there is regeneration of the blood-forming organs that were injured by X-rays. Table I summarizes the results of 3 experiments made with one transmissible strain of lymphomatosis (Rg 10) on the effect of irradiation before and after inoculation.
Irradiation after inoculation increased the percentage of successful inoculations of mice of a resistant stock from 0 to 16.7% and of mice of a moderately susceptible stock from 27.8 to 50%.
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