Which one of the following statements is true with regard to processing and presentation of protein antigens?
- In the class II MHC pathway, protein antigens in the cytosol are processed by proteasomes
- In the class I MHC pathway, extracellular protein antigens are endocytosed into vesicles and processed
- In the class I MHC pathway, transporter associated antigen processing (TAP) protein is required for translocating processed peptides generated in the cytosol
- Invariant chain in endoplasmic reticulum is involved in transport of peptides and loading of class I MHC