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)