Inhibition and enhancement of Friend leukemia virus by pyran copolymer.

Inhibition or enhancement of Friend leukemia virus disease could be produced by treatment of mice with the immunopotentiator, pyran copolymer. The result depended on the route of inoculation of the drug. Prophylactic administration of the drug i.p. retarded splenomegaly, reduced splenic foci, and increased survival time of mice infected with Friend leukemia virus. Conversely, when the same dose and regimen of pyran was administered i.v., splenomegaly was enhanced, splenic foci were increased, and survival time was decreased. Histopathological examination of the spleens of mice revealed that i.p. pyran administration caused a marked increase in the splenic marginal zone with some increase in erythropoiesis in the red pulp, while i.v. pyran administration did not markedly change the splenic marginal zone but caused an early and sustained increase in erythropoiesis in the red pulp.