the body’s natural defense against pathogenic organisms

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