I’m not quite sure this is accurate. Class I MHCs are expressed on all nucleated cells, while Class II are expressed on all Antigen-Presenting cells. MHC I essentially presents a signature of the body in the form of a protein. One of the ways that phagocytes recognise modified cells is by a change in the protein presented on this. The protein can differ due to many reasons, but one is due to a virus presenting a foreign protein on the MHC. If you want to make a suggestion of a better way to explain the concept in flashcard format (or further flashcards) then please let me know 
Will close this if no response in the next 48h.
Added deck-sgul-joe, rejected-suggestion and removed deck-sgul-joe, open-suggestion