First, we briefly describe the main cells involved in MS pathogenesis, both from neural tissue, including glial cells (such as microglial cells, oligodendrocytes, and astrocytes) and neurons, as well as cells from the immune system such as different T cell lineages, CD4+ (such as Th1, Th2, and Th17), CD8+, and Treg (CD4+CD25+FoxP3+), and also including a new participant, the adipocyte, a cell from the adipose tissue, focusing on their roles in MS. The gene discussed is CD4; the disease is myeloid sarcoma.