Transcription factor that specifically binds to the upstream regulatory region of type I interferon (IFN) and IFN-inducible MHC class I genes (the interferon consensus sequence (ICS)) (PubMed:25122610). Can both act as a transcriptional activator or repressor (By similarity). Plays a negative regulatory role in cells of the immune system (By similarity). Involved in CD8(+) dendritic cell differentiation by forming a complex with the BATF-JUNB heterodimer in immune cells, leading to recognition of AICE sequence (5′-TGAnTCA/GAAA-3′), an immune-specific regulatory element, followed by cooperative binding of BATF and IRF8 and activation of genes (By similarity). Required for the development of plasmacytoid dendritic cells (pDCs), which produce most of the type I IFN in response to viral infection (By similarity). Positively regulates macroautophagy in dendritic cells (PubMed:29434592). Acts as a transcriptional repressor of osteoclast differentiation factors such as NFATC1 and EEIG1 (By similarity).