A Graded-Response Assay for the Friend Leukemia Virus

Abstract

In Swiss mice inoculated intravenously with the Friend mouse leukemia virus, the mean log spleen weight at an arbitrary time after infection was a function of log virus dose. The dose-response function was S-shaped, with an upper shoulder or a plateau at high doses of virus, a linear phase, and a lower plateau with low doses of virus. Fitting of regression lines to the linear phase and calculation of the virus dosage corresponding to spleen-weight response of 500 mg. permitted reproducible quantitation of the agent. This procedure permits reasonable estimates of virus titer to be made on the basis of spleen-weight response to a single dilution of virus.