This study is designed to collect white blood cells from healthy volunteers. The cells will be used without identifiers in laboratory research to study the function of various types of white blood cells.

The white blood cells will be collected through a machine separation process called cytapheresis (cell removal). This machine process allows for the collection of larger amounts of white blood cells with less fluid and red blood cell loss to the donor.

Participants in this study are asked questions about their health and medical history. If this is satisfactory, an evaluation/screening visit is scheduled. This evaluation consists of an assessment of the arms to see if veins are large enough, an explanation of the study and obtaining study consent, the completion of a health history questionnaire, and blood and urine testing.

Participants are contacted 3-5 days after completion of the screening tests. If eligible, an appointment for the collection procedure is made.

The staff supervised collection procedure takes about two hours and involves placing a needle in each arm. Blood is drawn from one needle into the centrifuge and is spun to separate the cells. Small portions of the donor's white blood cells are removed (about a half pint of white blood cells including plasma over the two hour procedure). The donor's blood that is not being collected is returned to the donor through a needle in the other arm.

Donors are asked to schedule repeat donations. Donors are eligible to repeat this procedure every 56 days.

Inclusion Criteria:

• 18 years of age or older
• Generally healthy

Exclusion Criteria:

• Significant abnormalities on the health questionnaire or blood tests
• Pregnant or nursing women
• Inadequate vein access
• A severe infection within the past two months
• Taking medication that alters the white blood count
• Less than six weeks since participating in another research study
• Test results are positive for viral infections