Effects of Systemically Administered Hydrocortisone on the Immune System in Healthy Volunteers

Background: \- Corticosteroids have been used to treat inflammation and immune system diseases for decades. However, despite their widespread use, there is little information on the specifics of how corticosteroids affect the immune system in humans. The Center for Human Immunology, Autoimmunity, and Inflammatory Diseases is interested in studying how the steroid hormone hydrocortisone affects the immune system in healthy volunteers, and in doing so to understand how hydrocortisone given at different doses works in treating many immune and inflammatory conditions. Objectives: \- To evaluate the effects of hydrocortisone on the immune and inflammatory responses of healthy volunteers over the short and intermediate term (up to 28 days after administration). Eligibility: \- Healthy volunteers at least 18 years of age. Design: * Participants will be screened with a full medical history and physical examination, and blood and urine tests. At this visit, participants will be separated into two groups, with each group scheduled to receive a different amount of hydrocortisone during the study visit. * One week before the study visit, participants will provide a blood sample for baseline testing. * Participants will be admitted for a 24-hour inpatient stay that will involve frequent blood draws. Between blood draws, participants will be able to work, watch TV, walk around, and so on, and will be provided with regular meals. * Blood will be drawn 1 hour before the infusion of hydrocortisone. Participants will be divided into two further sets of groups with different blood draw schedules: * Groups 1 (lower dose) and 2 (higher dose) will have blood draws 1, 4, 8, 12, and 24 hours after the hydrocortisone infusion. * Groups 3 (lower dose) and 4 (higher dose) will have multiple blood draws over 24 hours, with timing based on data from the previous groups blood test results. * Participants will provide additional blood samples 7 and 28 days after the in-patient visit....