LCI Apheresis to Obtain Plasma or White Blood Cells

This study will collect blood plasma and white blood cells from individuals using a procedure called apheresis. Apheresis is a method of collecting larger quantities of certain blood components than can safely be collected through a simple blood draw or blood donation process. The blood components will be used in laboratory research studies to investigate aspects of infectious and immunologic allergic diseases. Patients 7 years of age and older who are currently enrolled in a NIH clinical research protocol may participate in this study. (Children between the ages of 2 and 6 may participate if they will benefit clinically from undergoing apheresis.) Family members of patients and normal healthy volunteers will also be enrolled. * For all adults and children weighing 55 pounds or more. Blood is drawn through a needle placed in an arm vein and circulated through a cell separator machine. The plasma and white cells are extracted, and the red cells are returned to the donor through a needle in the other arm. The procedure takes from 1 to 2 hours. * For children weighing less than 55 pounds. One unit (1 pint) of blood is drawn through a needle placed in an arm vein, similar to donating a pint of whole blood. The red blood cells are separated from the rest of the blood and returned to the donor through the same needle. This procedure requires only one needlestick and takes about 30 to 45 minutes to complete. In some circumstances, the procedure must be repeated one or more times in order to obtain large enough quantities of plasma or cells for study.