Hello, Welcome to HCM, Treating a severe form of Crohn s disease is challenging task for a clinician, I do understand the problems from your side. As per the details u have given, u are going towards using Tysabri ...right?? Tysabri contains NATALIZUMAB , which is an monoclonal antibody used in the treatments of severe cases with non responding to other drugs like steroids, other immunosuppressants like azathioprine, infliximab. But there is lot a controversies , risk Nd benefits with TYSABRI , iam giving the details as follows , 1. Treatment with Tysabri increases the risk of dangerous CNS infections like with JC virus and herpes virus..leads to a clinical condition called PML ..progressive multifocal leukoencephalopathy and herpes encephalitis leading to even death.. 2. Patients who were receiving this tysabri should be monitored carefully every 3months , to check whether they are acquiring the above CNS infections 3.prior MRI before starting surgery should be taken 4,. The chances of getting CNS infections will be doubled if the patient is already on immunosuppressive. So I advise you to consult a specialist and discuss the risks out of benefits before using the medicine... Hope this will help u a lot..bye