The bone marrow, B cells, and JC virus.
D001402:B-Lymphocytes / Q000821:virology*; D001853:Bone Marrow / Q000276:immunology* / Q000473:pathology / Q000503:physiopathology / Q000821:virology*; D016026:Bone Marrow Transplantation; D006801:Humans; D007577:JC Virus / Q000276:immunology / Q000302:isolation & purification