Macrophages genetically resistant to mouse hepatitis virus converted in vitro to susceptible macrophages

The original work indicating that resistant C3H cells could be made susceptible when treated with an extract of susceptible PRI cells was aimed at testing the question whether susceptibility could be directly transferred (7, 8) . The MLC experiments, on the other hand, suggested that the susceptibility of the macrophages was altered by a factor unrelated to susceptibility per se. To test this further, a preparation of supernatant fluid was made from mixtures of spleen cells of C3H and DBA, C3H and C57 black, and C3H and PRI mice. The effects of virus on C3H macrophages treated with these mixtures was then compared with The negative control, i.e. cells treated with fluid from C3H-C3Hss interaction, did not change in susceptibility. These results seem to add further evidence that susceptibility cannot be directly transferred. Viral Assay In Vivo and In Vitro. Previous work with the mouse macrophage system has shown that when very high multiplicities of MHV-PRI virus (i.e. virus adapted to PRI mice) were inoculated onto cultures of C3H-resistant macrophages, there emerged in some of the cultures a new virus that was adapted to the C3H cells, MHV-C3H (5). Thus, it was necessary to ascertain that the experiments did not simply reflect a heightened adaption of the virus to new host cells. This was tested by the following experiments: