Patient description: The patient is a 23-year-old man who came to the hospital with high blood pressure (175/95 mmHg) and signs of septicemia. He developed respiratory failure requiring mechanical ventilation and renal failure requiring hemodialysis. His blood smear showed microangiopathic hemolytic anemia and thrombocytopenia. His blood tests revealed elevated lactate dehydrogenase and reduced human complement C3 levels with a normal coagulation profile. He was diagnosed with atypical hemolytic uremic syndrome. He was treated with plasma exchange and corticosteroids. He has been previously vaccinated with meningococcal group ACWY conjugate vaccine and meningococcal group B vaccine. The genetic survey revealed ADAMTS13 >10%.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Severe Acute Respiratory Syndrome SARS SARS (ALL OF THE 1. Clinical diagnosis of SARS occurring greater than or equal to 3 months prior to screening. (objective documentation of SARS is not necessary) 2. The ability to understand and willingness to sign a written consent form and comply with study requirements and procedures. SARS (ALL OF THE 1. SARS Ab level greater than or equal to 1:80 2. Adequate clinical parameters (must meet all of the below): 1. Afebrile (temperature less than 38 degrees C) 2. Systolic blood pressure greater than 100 and less than 160 mmHg 3. Diastolic blood pressure greater than 50 and less than 100 mmHg 4. Heart rate between 50-100 beats/minute 5. Weight greater than or equal to 110 pounds (50kg) 3. Adequate laboratory parameters (must meet all of the below): 1. Hemoglobin greater than or equal to 12.5 g/dL for females or 13 grams/dL for males 2. HCT greater than or equal to 38% 3. Platelets greater than or equal to 150,000 x 10(3)/microL 4. Total serum protein greater than or equal to 6.0 grams/100 milliliters of blood 5. ALT less than 1.5 Upper limit of normal 6. Quantitative immune globulin levels (all of the following) Ig A greater than or equal to 90 mg/dL Ig G greater than or equal to 650 mg/dL Ig M greater than or equal to 35 mg/dL 4. Negative tests for blood borne pathogens (must meet all of the below): 1. Human Immunodeficiency Virus 1/2 Antibody (Anti-HIV1/2) negative 2. Hepatitis B virus surface antigen (HBsAg) negative 3. Hepatitis C virus antibody (anti-HCV) negative 4. RPR non-reactive 5. HTLV antibody 5. Adequate peripheral venous access for plasmapheresis (as judged by the examiner) DAY OF Afebrile (temperature less than 38 degrees C) 2. Systolic blood pressure greater than 100 and less than 160 mmHg 3. Diastolic blood pressure greater than 50 and less than 100 mmHg 4. Heart rate between 50-100 beats/minute 5. Blood hemoglobin level of greater than or equal to 12.5 grams/dL for females or 13 grams/dL for males 6. Total serum protein greater than or equal to 6.0 grams/100 milliliters of blood 7. Weight greater than or equal to 110 pounds (50kg) 8. RPR performed in the 4 months prior to the day of donation and non-reactive. 9. AST performed in the 4 months prior to the day of donation less than 1.5 upper limit of normal. 10. SARS antibody performed in the 4 months prior to the day of donation, and Ab titer greater than or equal to 1:80 11. Quantitative immune globulin levels performed in the 4 months prior to the day of donation (and all of the following) Ig A greater than or equal to 90 mg/dL Ig G greater than or equal to 650 mg/dL Ig M greater than or equal to 35 mg/dL  SARS Age less than 18 years old, or greater than 56 years old. 2. Signs of active respiratory infection including cough, dyspnea, or oxygen requirement. 3. Subjective fever in the last 3 days 4. History of headache with fever within the past 7 days. 5. Known history of congestive heart failure, pulmonary hypertension or other diseases in which the fluid shifts associated with apheresis present more than minimal risk. 6. Known history of bleeding diathesis or therapeutic anticoagulation. 7. Bilateral mastectomy or other relative contraindications to peripheral venous catheter insertion. 8. Within the last week has Taken traditional Chinese medicines Received hepatitis B vaccination. 9. Within the last 3 weeks has Received live-attenuated vaccines such as BCG, yellow fever, measles, mumps, poliomyelitis (oral), or live attenuated typhoid fever. 10. Within the last 4 weeks has Received rubella or varicella zoster (chicken pox) vaccination. 11. Within the last 6 weeks has Received standard IVIG for hepatitis A or other indications Received anti-tetanus toxoid or other passive immunizations with animal serum Been diagnosed with West Nile virus infection. 12. Within the last 8 weeks Was vaccinated with the small pox vaccine, or was in close contact with someone who was vaccinated (i.e., close family member). 13. Within the last 3 months has