1- One recent approach to vaccine development has been production of peptide vaccines. In these vaccines, antigenic peptides are injected instead of whole bacteria or viruses. Peptide vaccines have not been particularly useful against viral pathogens because viral infections require a CD8+ T cell mediated immune response. Why is a peptide vaccine unable to create such a response?

2- In type I insulin dependent diabetes, CD8+ T cells specifically target and destroy insulin producing b cells in the islets of Langerhans in the pancreas. How is MHC class I involved? “diabetes is not caused by a virus or intracellular bacterial infection”

3- The parasite, Toxoplasma gondii, invades cells and replicates inside its own vesicle which does not fuse with any cellular vesicles. Why is this parasite unable to be presented with class II MHC?