*2.13. Determination of Type I IFNs (IFN-*α/β*) Production by Immune Cells*

Quantification of IFN-α/β was carried out by a biological method in accordance with techniques based on the antiviral effect of interferons [40,41]. Briefly, mice splenocytes and peripheral blood leukocytes from 10 immunized mice of each group were stimulated in vitro by Newcastle disease virus (a standard IFN-α/β inducer) [42,43]. After virus inactivation, serial dilutions of the culture fluids were added to mouse fibroblast L-929 cell culture and 24 h later infected with encephalomyocarditis virus (EMCV). IFN-α/β activity was estimated as the highest reciprocal dilution that caused a 50% decrease in the cytopathogenic effect of 100 tissue culture infectious doses (TCID5O) per ml, and was expressed in international units per ml (IU/mL) using WHO International Standard Interferon alpha-2b (NIBSC cat. #95/566: https://nibsc.org/products/brm\_product\_catalogue/who\_standards.aspx).
