31.6 Diseases that Weaken the Immune System Goal/Objective Explain why individuals with weakened immune systems cannot fight off minor infections Describe in detail the

31.6 Diseases that Weaken the Immune System KEY CONCEPT When 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. –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 attacks and weakens the immune system. The human immunodeficiency virus (HIV) is a retrovirus. –is transmitted by mixing infected blood with a bodily fluid

31.6 Diseases that Weaken the Immune System HIV 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.

31.6 Diseases that Weaken the Immune System AIDS is acquired immune deficiency syndrome. –very low amount of T cells –opportunistic infections may lead to death HIV infection leads to AIDS.

31.6 Diseases that Weaken the Immune System If the immune system is weakened by leukemia or HIV, it cannot fight off pathogens like healthy people can! Pathogens like the common cold may become deadly Harmless bacteria may enter the body and the immune system cannot attack them

31.6 Diseases that Weaken the Immune System Next: On your paper you are going to create a timeline of an HIV infection using the table on page 962. Combine both of the tables on that page into a timeline. The dates on the timeline should line up with the dates in the graph. Above the timeline, draw what is going on in the person’s body at different times during the four and one-half years adding captions and labels to your drawings.