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31.6 Diseases that Weaken the Immune System
KEY CONCEPTWhen the immune system is weakened, the body cannot fight off disease.
31.6 Diseases that Weaken the Immune System
Leukemia is characterized by abnormal white blood cells.
– characterized by immature B-cells – causes weakened immune system
• Leukemia is cancer of the bone marrow.
31.6 Diseases that Weaken the Immune System
• Leukemia leads to opportunistic infections.– occur because white blood cells cannot fight
infections– if immune system were healthy, it would fight these
infections
31.6 Diseases that Weaken the Immune System
HIV targets the immune system.
• The human immunodeficiency virus (HIV) is a RNA retrovirus. – attacks and weakens the
immune system– is transmitted by mixing
infected blood with a bodily fluid
31.6 Diseases that Weaken the Immune System
• HIV infection leads to AIDS.
HIV
T celldeadT cell
antibody
activatedB cell
– HIV reproduces in and destroys T cells.– The body cannot replace T cells fast enough.– T cells cannot help in immune responses.
31.6 Diseases that Weaken the Immune System
• AIDS is acquired immune deficiency syndrome. – several opportunistic infections = infections
succeed because T cells are gone—they take opportunity to survive
– very low amount of T cells (less than 200 T Cells)
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