• INCLUSION CRITERIA:

Individuals of African descent of age 18 or greater

Normal renal function: creatinine less than 1.5 mg/dl and proteinuria less than 1+

Normal liver function: bilirubin less than 1.5 mg/dl and transaminases within normal limits

For CONTROL subjects: WBC within normal range (3,300 -9,600/mm(3)), granulocytes greater than or equal to 1,500/mm(3), platelets greater than 150,000/mm(3), hemoglobin greater than 11.5 g/dL, and normal MCV

For BENIGN ETHNIC NEUTROPENIC subjects: two blood counts, at least 1 month apart, in the last 6 months, with granulocytes less than 1,500/mm(3), platelet greater than 150,000/mm(3), hemoglobin greater than 12.5 g/dL, and normal MCV

Female volunteers of childbearing age should not be pregnant

Meets NIH Department of Transfusion Medicine (DTM) eligibility criteria for blood component donation for in vitro research uses (negative serologic tests for syphilis, hepatitis B and C, HIV, and HTLV-1)

Ability to give informed consent to participate in the protocol

EXCLUSION CRITERIA:

Any underlying hematologic disorder including anemia, thalassemia, and sickle cell trait or disease

Current use of corticosteroids, e.g. prednisone, dexamethasone, or hydrocortisone. Corticosteroids must be discontinued at least one month prior

Active or chronic viral, bacterial, fungal, or parasitic infection. Any antibiotic use should be discontinued at least one month prior

History of autoimmune disease, such as rheumatoid arthritis or systemic lupus erythematosus, or positive anti-nuclear antibody (ANA ELISA) of 3 E.U. (ELISA units) or greater

Low B12 or folate levels, or abnormal thyroid function tests

History of cancer or chemotherapy, except squamous carcinoma of the skin and cervical carcinoma in situ

Pregnant woman or positive urine pregnancy test

History of clinically significant cardiovascular disease (cardiology consultation may be obtained when clinically indicated).

Any positive serum screening test as listed below

Allergy to G-CSF or bacterial E. coli products