The failing immune system.
D000368:Aged; D000375:Aging; D000917:Antibody Formation; D001327:Autoimmune Diseases / Q000276:immunology; D005260:Female; D006801:Humans; D007109:Immunity; D007111:Immunity, Cellular; D007121:Immunocompetence; D008297:Male; D011247:Pregnancy