The Stanford Parkinson's Disease Plasma Study

Inclusion Criteria: * A diagnosis of clinically probable or established Parkinson's Disease (MDS criteria) * Subject must be on a stable dose of dopaminergic medication and/or Deep Brain Stimulation (DBS) parameters for at least 4 weeks prior to screening and for the duration of the study * Subject must be competent to sign consent * Subject must be willing to commit to being available for testing and infusions for 6 consecutive weeks (2 testing consecutive weeks, 4 infusion consecutive weeks) followed by two visits a month after final infusion. * The availability of a study partner who knows the patient well and is willing to accompany the subject to all trial (optional if participant is able to consent and travel by self) Exclusion Criteria: * The participation in any other interventional clinical trial * The inability to travel to Stanford * Inability to walk without assistance in the off or on medication state * The clinically determined presence of dementia * A clinical suspicion/diagnosis of Multiple System Atrophy (MSA), Progressive Supranuclear Palsy (PSP), Lewy Body Dementia (LBD), Essential Tremor (ET) * Subject's pregnancy or likelihood of pregnancy within the next 6 months. * Subject's positive test results for Hepatitis B, Hepatitis C or HIV at screening * Any other condition or situation that the investigator believes may interfere with the safety of the subject or the intent and conduct of the study * Subject's medical history of: Stroke Anaphylaxis Gout- may cause an increase in uric acid Prior adverse reaction to any human blood product Any history of a blood coagulation disorder or hypercoagulability Congestive heart failure Uncontrolled hypertension Renal failure Prior intolerance to intravenous fluids Recent history of uncontrolled atrial fibrillation immunoglobulin A deficiency (by history) * Subject's relation to medications or other treatments: * Any concurrent use of an anticoagulant therapy. Antiplatelet drugs (e.g., aspirin or clopidogrel) are acceptable. * The use of Inosine, which may alter urate levels * Initiation or change in the dosage of a cholinesterase inhibitor or memantine during the trial. A participant already on a cholinesterase inhibitor or memantine must be on a stable dose for at least one month prior to Screening. * Concurrent participation in another interventional treatment trial for Parkinson's disease. If there was prior participation, the last dose of the investigational agent must have been at least 6 months prior to Screening. * Treatment with any human blood product, including intravenous immunoglobulin, during the 6 months prior to Screening or during the trial. * Concurrent daily treatment with benzodiazepines, typical or atypical antipsychotics, long-acting opioids, or other medications that, in the investigator's opinion, interfere with cognition. Intermittent treatment with short-acting benzodiazepines or atypical antipsychotics may be permitted, provided that no dose is administered within the 72 hours preceding any cognitive assessment.