This protocol is being submitted to consolidate, update, and expand two previously approved protocols (77-C-0066 and 82-C-0044) into a single protocol. The purpose of this study is to examine the factors involved in the regulation of the immune system of healthy individuals and to define the abnormalities in this regulation that underlies the immunological disorders of patients with a variety of immunodeficiency and malignant disorders. The studies will include the ex vivo phenotypic and functional analysis of the network of cells involved in humoral and cellular immune responses, and in vivo testing for the capacity to make delayed-type hypersensitivity and humoral responses following immunization with a variety of antigens. Individuals to be studied will include patients with a variety of malignancies and patients with primary and secondary immunodeficiency disorders. Selected family members or family members known to be genetic carriers of certain immunodeficiency diseases as well as normal, unrelated individuals will also be studied. A small number of procedures will be used including analysis of blood obtained by phlebotomy, apheresis, skin testing and recall antigens and immunization to assess humoral immunity.