the body’s natural defense against pathogenic organisms
TRANSCRIPT
The body’s natural defenseAgainst pathogenic organisms
Nonspecific Defense Against a Pathogen –Physical and Chemical Barriers
skinEyelashes and eyebrows
tears
mucus
Salivary glands
Stomach acid
Non-barrier, nonspecific defenses
fever
Inflammation turns red from increased blood flow to damaged area
Infected cut – wbc battled bacteria – creates pus
Swelling indicates the body is sending more blood and lymph to the affected area to help correct the injury or fight the pathogen
Phagocytes - WBC (white blood cells)
Eat pathogens
Alert other immune system cells that a pathogen is present
The Lymphatic System –series of vessels carrying lymph and
phagocytes
Natural Killer Cells – WBC that kill virus-infected cells
This target cell then dies along with the viruses inside it!
Interferons – small proteins that cause normal, uninfected cells to produce antiviral compounds that
interfere with viral replication; they also stimulate macrophages
and NK into action.
Antigen-Antibody Relationship
A foreign substance that causes the production of an antibody to destroy it is called an ANTIGEN
An ANTIBODY is produced in response to detection of a foreign substance like the proteins on a virus or bacteria cell.
Specific Cellular Defense
B-cell eats pathogen, breaks it apart, and displays its proteins on the surface of the B cell.
Helper T cell, plasma cell, and memory B cells then are involved in the antibody response and remembering it for the next time.
1. Macrophage (white blood cell) consumes a virus.
virus
macrophage
2. Macrophage digests virus and displays viral antigens on its
surface
Antigen
3. One helper T cell recognizes the antigen and binds to the
macrophage
Helper t cell
4. Chemicals (interleukin-1 and tumor necrosis factor), made by the macrophage and others
(interleukin-2 and gamma interferon) made by the T cell, allow intercellular communication
5. These chemicals instruct other helper T cells and killer T cells to multiply.
The B cells multiply and produce antibodies.
Killer t cell antibody
Helper t cell
B cell
6. Killer T cells destroy cells that have been infected by the virus (and
unfortunately some uninfected cells, too)
Killer t cell
7. Antibodies released by B cells binds to antigens on viruses – this makes it easier for
macrophages to eat the viruses and helps destroy the viruses themselves.
8. When infection is controlled, suppressor T cells stop the reaction. Memory cells remain
to respond quickly if same virus attacks again
Memory cell
Suppressor t cells
Memory b cell
Allergies – the immune system makes a mistake!
• Triggered by noninfectious agents such as pollen or pet dander
• Causes an inflammatory response that could be runny nose, sneezing, wheezing, hives, etc.
• Can be developed after years of exposure to the allergen – the body seems to reach a critical exposure level.
The End