Tissue Specificity of Interferon Prepared in Various Tissue Cultures

The activity of ITFs prepared in 8 mammalian cell cultures and CAM culture was determined in homologous and heterologous systems. The data indicate that HEK ITF exhibits the greatest heterologous activity under the conditions of the test. Primary RK cells were the most sensitive for detection of heterologous ITF from mammalian source. Sensitivity of the assay method is increased greatly by maintaining a viral challenge of 30 or less TCID50. Under this condition, MK(Rh) ITF could be assayed in homologous as well as heterologous cells as could RK ITF. The production of ITF in HAE and PK cultures is, to our knowledge, the first reported case of production in cells not susceptible to influenza virus infection.