Fv1-like restriction to N-tropic virus infection in nonmurine cells. Cells were infected with equal titers of N- and B-tropic virus. Twenty-four hours later, the numbers of infected cells were determined by FACS analysis. Log B/N values were obtained by dividing the percentage of cells infected with N-tropic virus by the percentage cells infected with B-tropic virus and calculating the log value. Cells with Fv1n-like phenotype therefore have negative values and those with Fv1b-like phenotype have positive values. Values close to zero represent Fv1-null lines. Errors are standard error. Mu, mouse; Rt, rat; SH, Syrian hamster; CH, Chinese hamster; M, mink; F, ferret; R, rabbit; Ca, cat; D, dog, P, pig; C, cow; AGM, African green monkey.