Human fibroblast and leukocyte interferons show different dose-response curves in assay of cell protection

Preparations of human fibroblast and leukocyte interferons of similar potency show markedly different dose-response curves in an assay which measures the degree of protection of tissue cultures against virus c.p.e. The effect is observed with both vesicular stomatitis virus (VSV) and Mengovirus, and is not altered by purification of the interferons.