CD4 T cells or CD8 T cells are activated by reacting with MHC molecules.[58] T cells can contribute to graft rejection by activating macrophages, which cause tissue injury and fibrosis.[59] Similarly, CD+4 or CD+8 T cells are important in the development of MS.[60,61] Immune cells have destructive effects on CNS myelin and oligodendrocytes.[62] Therefore, it is unsurprising that a majority of MS risk genes are enriched in hsa05330 (allograft rejection). The gene discussed is CTLA4; the disease is myeloid sarcoma.