1. KEY CONCEPT When the immune system is weakened, the body cannot fight off disease.

2. Leukemia is characterized by abnormal white blood cells.
Leukemia is cancer of the bone marrow.
characterized by immature white blood cells
causes weakened immune system

3. Leukemia leads to opportunistic infections.
occur because white blood cells cannot fight infections
if immune system were healthy, would fight these infections

4. HIV targets the immune system.
The human immunodeficiency virus (HIV) is a retrovirus.
attacks and weakens the immune system
is transmitted by mixing infected blood with a bodily fluid

5. HIV infection leads to AIDS.
T cell
dead T cell
antibody
activated B cell
HIV reproduces in and destroys T cells.
The body cannot replace T cells fast enough.
T cells cannot help in immune responses.

6. AIDS is acquired immune deficiency syndrome.
several opportunistic infections
very low amount of T cells