The relationship between serum interferon and an inhibitor of mouse haemopoietic colonies in vitro.

When mice are inoculated with Poly I—Poly C or influenza virus an inhibitor of haemopoietic colony forming cells appears in the serum. The colony inhibiting activity of whole serum is shown to be directly proportional to the interferon titre. Interferon and colony inhibitor are also shown to have the same properties with regard to molecular size and sensitivity to heat, pH and trypsin.