Diverse intracellular pathogens activate type III interferon expression from peroxisomes.

Abstract

Type I Interferon (IFN) responses are considered the primary means by which viral infections are controlled in mammals. Despite this view, several pathogens activate antiviral responses in the absence of Type I IFNs. The mechanisms controlling Type I IFN-independent responses are undefined. We have found that RIG-I like Receptors (RLRs) induce Type III IFN expression in a variety of human cell types, and identified factors that differentially regulate Type I and III IFN expression. We identified peroxisomes as a primary site that initiates Type III IFN expression, and revealed that the process of intestinal epithelial cell differentiation upregulates peroxisome biogenesis and promotes robust Type III IFN responses in human cells. These findings highlight the interconnections between innate immunity and cell biology.