32.1: First Line of Defense
The skin acts as both a physical and chemical barrier
to prevent pathogens from entering the body.
In 40 minutes, your body loses and replaces about 1
million skin cells.
Tears, saliva, and mucous membranes help keep pathogens
from entering the body.
Inflammation involves a series of events designed to
fight off an infection.
Macrophages (white blood cells known as phagocytes)
play an important role in destroying pathogens and dead cells.
Pathogens are things that cause diseases.
Antigens are molecules that trigger a defensive response
in your system.
Marker proteins on cells allow macrophages to recognize
pathogens and other foreign substances (so they can destroy them).
32.2: The Immune Response
Macrophages engulf and consume invading pathogens (recognized
as foreign because of their marker proteins).
The immune response involves 2 kinds of white blood
cells: T cells and B cells.
Helper T cells stick to macrophages that display the
antigen s from pathogens they have consumed. Once stuck, the helper
T cell promotes the production of killer T cells.
Killer T cells destroy pathogens by pinching holes
in their cell membranes.
Suppressor T cells stop the immune response once the
pathogens have been destroyed.
B cells produce antibodies that tie up the pathogens
so the macrophages can easily destroy them.
Memory B cells stay around after the pathogens are
destroyed, in case they are needed if the pathogen comes back reappears.
Vaccines help memory B cells to develop so that the
body remembers how to fight off infections in the future.
BUT, vaccines arent effective against rapidly
evolving viruses (like the common cold).
Protein antigens on red blood cells account for the
different blood types.
32.3: Immune System Failure
An allergy involves the response of the immune system
to a harmless (to the average person) antigen.
In an allergic reaction, you release histamines.
Histamines cause capillaries to swell and release fluid.
To stop this, many allergy medicines contain antihistamines
that stop histamine action.
Autoimmune diseases result when the immune system starts
to attack its own body cells.
Autoimmune diseases include multiple sclerosis, type
1 diabetes, and rheumatoid arthritis.
The immune system sometimes fails to destroy cancer
cells that arise from mutations or as a result of carcinogens.
A mass of cancerous cells is called a tumor.
HIV is transmitted in body fluids.
HIV destroys T cells, resulting in AIDS. |