Radiation Sensitivity and Post-irradiation Repair of Mouse Lymphatic Cellsin Vivoandin Vitro. A Study with the Parent to F1Hybrid Graft-versus-host Reaction

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Abstract
The killing-effect of lymphatic cells from one of the parental strains in F1 hybrid recipients was used as a graft-versus-host reaction in determining the percentage of lymphatic cells which maintained their reproductive integrity (survival percentage) after x-irradiation. The same radiosensitivity of lymph-node cells (D0 circa 85 R) was found when the cells were irradiated either in the donor (before the suspension was prepared), in vitro, or in the recipient within 4 hours after injection. If irradiated 24 hours after inoculation the cells were more resistant, but it was not certain whether this really meant an increase in the resistance of the cells or whether a proliferation of cells was involved. Cells derived from mice presensitized by C57BL skin transplants showed the same sensitivity as normal lymph-node cells. No difference was found in radiosensitivity of lymphatic cells from lymph nodes, spleen or peripheral blood. The oxygen-enhancement factor of lymph-node cells was about 2·7. It was concluded that lymphatic cells participating in the graft-versus-host reaction had a similar sensitivity for x-rays as other mammalian cells. Differences in radiation sensitivity of the immune response in whole animals relative to the time of irradiation and antigen injection, and differences in radiosensitivity of the primary and secondary immune response are difficult to explain by variations in radiosensitivity of the stem cells giving rise to the immune reactions.