In recent decades, hematologists have noticed that persons of African descent sometimes have lower white blood cell counts of a certain type, called granulocytes. These cells help to fight infections. The lower number of granulocytes in this situation does not appear to lead to more infections, and these individuals do not have any symptoms. This condition is called benign ethnic neutropenia (BEN), and is observed in a small percentage of individuals of African descent. This study will investigate the condition by studying people with and without BEN.

The goals of this study are to:

1. identify individuals of African descent with BEN.
2. determine the effects of two drugs, G-CSF and dexamethasone, on granulocyte production and movement.
3. determine whether there are differences in those with and without BEN in the way genes are stimulated after the administration of G-CSF and dexamethasone.

Study participants will be asked to interview with the research team, undergo physical exams, donate a blood sample, and receive G-CSF by injection, followed by dexamethasone (orally) about three weeks later. They also will be required to undergo apheresis three times, a procedure in which blood is drawn from a donor and separated into its components. Some components are retained for research analyses, such as granulocytes, and small amount of blood; the remainder is returned by transfusion to the donor. This procedure will be required of participants before they receive G-CSF, the day after they receive G-CSF, and the day after they receive dexamethasone. Gene messages (mRNA will be isolated from granulocytes, and analyzed to better understand granulocyte growth and movement.

Benign ethnic neutropenia (BEN) is defined by peripheral blood absolute neutrophil count less than 1.5 x 10(9) per liter without an increase in infections. This condition has been described in individuals of African descent. Although these individuals have normal myeloid maturation on bone marrow examinations, they appear to release fewer neutrophils into the circulation when stimulated by hydrocortisone, compared to normal controls.

This suggests that there may be differences in the regulation of neutrophil release or trafficking. In the past decade, granulocyte-colony stimulating factor (G-CSF) has been widely used in a variety of clinical settings, from patients with chemotherapy-induced neutropenia to normal volunteers for peripheral blood stem cell collection. G-CSF, however, has not been used in individuals with BEN. Furthermore, gene expression in neutrophil proliferation and trafficking has not been studied in these individuals. The purpose of this study is to identify individuals with BEN; to characterize and compare neutrophil response to dexamethasone and G-CSF; to compare the pattern of neutrophil gene expression by microarray analyses; to determine if mutations are present at the DNA level to account for gene expression pattern differences, in individuals of African descent with and without BEN at baseline, post dexamethasone, and post G-CSF stimulation and to follow the natural history of BEN.

• Ash RC, Mendelsohn LA, Marshall ME. Hemopoietic marrow function in chronic neutropenia of blacks: cure of aplastic anemia by allogeneic marrow transplantation from a neutropenic sibling donor. Am J Hematol. 1986 Jun;22(2):205-12.
• Haddy TB, Rana SR, Castro O. Benign ethnic neutropenia: what is a normal absolute neutrophil count? J Lab Clin Med. 1999 Jan;133(1):15-22. Review.
• Mason BA, Lessin L, Schechter GP. Marrow granulocyte reserves in black Americans. Hydrocortisone-induced granulocytosis in the "benign" neutropenia of the black. Am J Med. 1979 Aug;67(2):201-5.

• 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