• Assessment of immune responses [ Time Frame: throughout study ] [ Designated as safety issue: No ]
  
• Clinical response in PND patients who are treated with Tacrolimus and Prednisone [ Time Frame: throughout study ] [ Designated as safety issue: No ]
  

• Collection and archiving of serum and lymphocytes for future studies on the mechanism of neuronal autoimmunity. [ Time Frame: end of study ] [ Designated as safety issue: No ]
  

patients may stay either in-hospital while being treated with Tacrolimus, receive treatment as an outpatient, or a combination of the two. Additionally, patients who are too sick to be treated at Rockefeller University (eg. patients actively seizing), but are in need of urgent treatment, may be treated at either Memorial Sloan-Kettering Cancer Center or New York-Presbyterian Hospital in conjunction with MDs there. Dr. Robert Darnell, being credentialed at both institutions, will be the primary person responsible for monitoring all portions of the study performed at MSKCC and New York-Presbyterian Hospital. During treatment, patients will undergo blood draws, at set intervals (see section g below), clinical evaluation, possibly repeat leukapheresis or large volume blood draw, and lumbar puncture (see below). Since many patients live far away from NY, some of these procedures may be performed by RU staff or in conjunction with their local MDs.

Patients who are terminated from Tacrolimus treatment after 7-21 days will be followed up as outpatients for evaluation of their neurologic and medical status. Wherever possible, these patients will be seen on days 3 and 10 post treatment termination, and then on a biweekly basis for two months. Since many patients live far away from NY, they may instead be monitored in conjunction with their local MDs. Patients who show a definite clinical response to Tacrolimus may be maintained on a therapeutic dose for up to one year, and will be followed as outpatients. For patients receiving retreatment, they may be treated as inpatients or on an outpatient basis, at the discretion of the PI, on the same schedule as patients being treated initially (see 10.g.). Long term improvement or decline in neurologic function will be objectively assessed by neurologic exam, which will be quantified by use of the Karnofsky scale (a measure of functional neurologic status). Since the vast majority of Hu patients decline over a 6-12 month period following diagnosis, a stable or improved Karnofsky score over such a time period will be taken as a measure of successful treatment. Repeat lumbar puncture (up to eight per year) and leukapheresis or large volume blood draw (approx. 100 cc) may be performed (up to four of each per year), especially in the setting of neurologic change, to assess the immune responses to the medications.