Why do normal t cells, which recognize foreign peptide antigens bound to self mhc molecules, react strongly against the allogeneic mhc molecules of a graft?

T cells are associated with blood cells fighting infection. Allogenic mhc molecules are immonologically incompactible cell surface proteins essential for aquired immune system. The t celss react strongly against such mhc molecules of a graft because they resemble self MHC plus a foreing peptide.