Healthy volunteers and patients with confirmed or suspected rheumatic or kidney disease who are 18 years of age or older may be eligible for this study. Patients must be participating in a current protocol of the National Institute of Arthritis and Musculoskeletal and Skin Diseases or the National Institute of Digestive, Diabetes and Kidney Diseases. All candidates will be screened with a history, physical examination, and blood tests for hepatitis B and C and HIV infection. Women of childbearing age will be tested for pregnancy. Routine blood tests will be done in all volunteers, and in patients where needed. Pregnant women and people who test positive for hepatitis or HIV may not participate.