AbstractTreatment of mice with the long‐lived bone‐seeking radioisotope89Sr results in the selective irradiation and destruction of the bone marrow. This is accompanied by a marked reduction in natural killer cell activity against YAC‐1 lymphoma NK(YAC‐1). To test for the presence of cellular suppressors of NK(YAC‐1) in89Sr‐treated mice,in vitroandin vivocell mixture protocols were used.In vitro, we did not observe any specific inhibitory effect of spleen cells from89Sr‐treated mice on NK(YAC‐1) activity of normal spleen cells. The NK(YAC‐1) activity of89Sr‐treated mice, measuredin vivoby their ability to clear radiolabeled YAC‐1 cells from the lungs, was impaired. However, spleen cells from89Sr‐treated mice, when adoptively transferred with normal spleen cells, failed to inhibit the NK(YAC‐1) activity of the latter in the lung clearance assay. Further, when normal spleen cells were injected into89Sr‐treated mice, the ability of the transferred cells to mediatein vivoactivity was not suppressed in the89Sr‐treated host. These experiments support the suggestion that the low NK(YAC‐1) activity in89Sr‐treated mice is not mediated by suppressor cells, but may be due to the destruction of the marrow microenvironment which is essential for the generat
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