Apoptosis, or programmed cell death, can be triggered in immune cells like Molt-4 and Ana-1 by exposure to fission fragment ^147Pm. This study estimated the amount of ^147Pm absorbed by these cells over time. When internally irradiated with ^147Pm, these immune cells showed nuclear fragmentation, DNA chain breakage, and formation of apoptotic bodies. The radioactive material was able to penetrate the cell membrane and cause cell death. This research provides evidence that Molt-4 and Ana-1 immune cells undergo apoptosis when exposed to ^147Pm.