Final answer:
The IFN response can be activated by both cytosolic and endosomal receptors, which are involved in pathogen recognition and antiviral responses within cells.
Step-by-step explanation:
The IFN response (Interferon response) can be activated by both cytosolic receptors and endosomal receptors. These receptors are involved in the recognition of pathogens and the initiation of antiviral responses. Cytosolic receptors can detect viral RNA inside the cell, while endosomal receptors can recognize viral components within endosomes, which are vesicles inside the cell.
Receptors are protein molecules in the target cell or on its surface that bind to ligands. Internal receptors, also known as intracellular or cytoplasmic receptors, are found in the cytoplasm of target cells and respond to hydrophobic ligand molecules that are able to travel across the plasma membrane. Once inside the cell, these molecules can influence gene expression by mediating the synthesis of mRNA (transcription).
In conclusion, the answer to the question is c) Both cytosolic and endosomal receptors.