So one type of T cell is the AlphaBeta T cell. And we call this an alphabeted T cell because it contains a T cell T cell receptor that has an alpha subunit and a beta subunit. Now, in our discussion on AlphaBeta T cells we said that AlphaBeta T cells can only bind to either the MHC class one or the MHC class two complex found on some antigen presenting cell of our immune system. So recall that antigen presenting cells are cells such as macrophages, dendritic cells and belymphocytes that engulf antigens and then present those antigens to the T lymphocytes by using their major histocompatibility protein complexes found on the membrane. And we have these two different classes of these major histocompatibility complexes. The class one are responsible for differentiating between infected cells and healthy cells.