Class 1⃣ MHC are found on the cell surface of ALL nucleated cells + platelets. Their role is to present intracelleular peptide fragments to CD8 #Tcells
Class 2⃣ MHC are found on the surface of "pro" antigen presenting cells (APCs), e.g. dendritic cells, B cells, mononuclear phagocytes, some endothelial cells.
They present extracellular peptides that are phagocytosed, digested in lysosomes ➡️ loaded onto class 2⃣ molecule