Ultrastructure and virus particles of L1210/Mes. A hamster-adapted murine leukemia.

The ultrastructural features and virus particle content of L1210/Mes., the hamster-adapted strain of murine leukemia L1210, has been studied in cheek pouch tumors and cell cultures. In comparison with the parental murine tumor in culture, L1210/Mes. has experienced certain morphologic alterations, such as a striking increase in cell size, enlarged and more bizarre nuclei, and an increase in the number of lysosome-related structures. Type A (intracytoplasmic and intracisternal) and type C virus particles could be demonstrated in cell cultures of murine leukemia L1210, and in cheek pouch grafts and cell cultures of L1210/Mes. No. "H" (or "R") hamster-associated virus particles, however, could be distinguished in L1210/Mes. tumors or in vitro cultivated cells. It appears that a murine lymphoma capable of serial propagation in a xenogeneic host permits the replication of virus particles structurally indistinguishable from those indigenous to it.