This study will determine the biochemical and genetic causes of inherited immune diseases affecting lymphocyte homeostasis. Lymphocytes are a type of white blood cell that fights infections. Normally, the body keeps a precise balance in which lymphocyte growth is matched by lymphocyte death. People with constantly enlarged lymph nodes or spleen, along with autoimmune disease, immunodeficiency, lymphoma, or other immune problems affecting lymphocytes may have an abnormality of the immune system in the cell growth and cell death processes that regulate lymphocyte homeostasis. Patients who have, or are suspected of having, an inherited lymphocyte homeostasis or programmed cell death susceptibility syndrome may be eligible for this study. Relatives of patients are also included. Participants' (patients and relatives) medical records are reviewed and blood samples are drawn for studies to identify genes involved in immune disorders. Tissues that have been removed from patients for medical reasons, such as biopsied tissues, may be examined for tissue and DNA studies. Relatives are studied to determine if some of them may have a very mild form of lymphocyte homeostasis disorder. Patients who have an immune problem that the researchers wish to study further will be invited to donate additional blood samples at irregular intervals (at least once a year) and to provide an update of their medical records at the same time.