MHC molecules are classified into two main classes: MHC Class I and MHC Class II. MHC Class I molecules are found on almost all nucleated cells and present endogenous peptides (typically from inside the cell) to CD8+ T-cells. MHC Class II molecules are found on antigen-presenting cells (APCs) like dendritic cells and present exogenous peptides (from outside the cell) to CD4+ T-cells.
