This study collects specimens from volunteers for use in studies by NIAID's Vaccine Research Center. A number of different types of specimens or samples can be collected, including blood, urine, body fluids or secretions, skin swabs, or skin biopsies. The samples are used for medical research, including the study of HIV, hepatitis, and other diseases; immune system responses, such as responses to vaccinations or infections; and for research on vaccine development. Blood samples may be collected either by ordinary blood drawing (phlebotomy) or by apheresis, a procedure for collecting a larger quantity of blood cells or plasma than would be possible through simple blood drawing. For this procedure, the participant lies on a recliner or couch. Blood is removed through a needle in the vein of one arm and spun in a machine that separates out the desired component (plasma or white blood cells). The remainder of the blood is returned either through the same needle or through a needle in the other arm. The procedure takes about 1 to 3 hours. Volunteers who are 18 years of age and older, including participants in other NIH research protocols, may be eligible. Individuals who have a condition that the research staff considers a reason not to make a sample donation will be excluded from the study. Participants may have only one sample collected or may be asked to undergo repetitive sample collection procedures, depending upon the requirements of the particular research project for which the samples are being collected. Each individual's enrollment is for a 1-year period, which can be extended. ...