Bioassay for the measurement of type-I interferon activity.

Type I interferons are critical cytokines produced by the host innate immune response to viral infection. They act collectively to initiate expression of a multitude of antiviral genes that serve to inhibit viral replication and spread. Despite the great importance of interferons to the host response to viral infection, assays to measure their presence can be costly and require a great deal of optimization for success. Here, we describe an inexpensive approach for the determination of murine type I interferon activity in a given set of samples, which is based on using 50 % protection of a cell monolayer from virus-induced cytopathic effects as an endpoint measurement. The following protocol allows for the accurate and sensitive measurement of interferon activity without the use of highly specialized equipment or reagents.