HSC, lymphocytes, monocytes and granulocytes will be used for laboratory research studies that include: Delineating the pathophysiology of inherited immune deficiencies; Delineating the physiology of and improving engraftment of hematopoietic stem cells; Determining how hematopoietic stem cells may be maintained in ex vivo culture without losing pluripotent potential; Delineating the molecular mechanisms responsible for lineage specific differentiation; Developing efficient methods for gene transfer into hematopoietic stem cells for corrective gene therapy; Developing methods for restoration of function in defective peripheral blood monocytes and/or granulocytes; Further characterization of peripheral blood monocytes and/or granulocytes from patients with PID.