Opinion ID: 203426
Heading Depth: 2
Heading Rank: 1

Heading: TYSABRI and Its Effects

Text: TYSABRI [2] is a drug developed, manufactured, and marketed by Biogen for the purpose of treating autoimmune diseases, especially multiple sclerosis (MS), Crohn's disease, and rheumatoid arthritis. [3] Generally, autoimmune diseases cause the human body's immune system to attack otherwise healthy tissues in the body. TYSABRI works, in part, by preventing migration of white blood cells throughout the body. In MS, for example, the arrival of white blood cells to the central nervous system causes inflammation, which in turn destroys nerve fiber and the fatty tissue surrounding nerve fiber, creating lesions or plaques in the nervous system. Over time, these plaques disrupt the function of the nervous system, causing the various symptoms of MS, including progressive physical disability and eventual cognitive impairment. TYSABRI prevents the white blood cells from migrating to the central nervous system, relieving the inflammation and mitigating the symptoms of MS. Another effect of TYSABRI's mechanism of action is that the drug could prevent white blood cells from migrating to places in the body where they are needed. This may leave a patient vulnerable to opportunistic infections, which occur when ordinarily benign organisms infect individuals with impaired immune systems. While a healthy immune system would prevent these organisms from causing illness, an impaired immune system may not be able to stave off infection. One such opportunistic infection is progressive multifocal leukoencephalopathy (PML), a usually fatal disease of the central nervous system caused by the JC virus. The JC virus is latent in the kidneys of almost all adults, and invades the brain and causes PML only when the immune system is severely impaired.