 CD80 is an especially important component in dendritic cell licensing and cytotoxic T-cell activation.When the major histocompatibility complex class II (MHC class II)- peptide complex on a dendritic cell interacts with the receptor on a T helper cell, CD80 is up-regulated, licensing the dendritic cell and allowing for interaction between the dendritic cell and CD 8+ T-cells via CD28.This helps to signal the T-cell differentiation into a cytotoxic T-cell.