As a major part of the adaptive immune system, T-cells scan the intracellular environment in order to target and destroy infected cells. Small peptide fragments, representing the entire cellular content, are transported to the cell surface as pMHCs, allowing T-cell surface expressed antigen specific TCRs to scan for foreign signals. T-cells interact with a large number of different cell types and recognise a diverse array of pathogens. This diversity has lead to distinct antigen recognition pathways which generate the appropriate T-cell response. T-cell activation can lead to a number of immune responses such as antibody production, activation of phagocytic cells and direct cell killing. In this way, the appropriate immune response for different types of diseases is implemented.