The Body’s Lines of Defense

Pathogens

Pathogens are disease causing organisms.

The body has 3 lines of defense.

The first 2 lines of defense are non specific and the 3rd line is specific

First Line of Defense- Skin

Skin is the largest organ in our body and provides a barrier that normally cannot be penetrated by bacteria and viruses.

The skin uses acidic secretions that contain Lysozymes (found in tears, saliva, mucous secretions, and perspiration), which keep it at a pH range of 3 to 5.

This is acidic enough to inhibit the growth of microbes.

First Line of Defense- Mucous

Mucous can be found in the respiratory passage.

Cells in the trachea produce a mucus that traps microbes before they reach the lungs.

Corrosive acids in the stomach destroy most of the invading microbes carried into the body with food.

Second / Third Line of Defense- Leukocytes

A second line / third line of defence acts if the invader enters the body.

Leukocytes are white blood cells that may engulf invading microbes or produce antibodies.

Leukocytes that take part in phagocytosis are part of the bodies second line of defense and are non-specific.

Leukocytes that produce antibodies are specific and part of the body’s third line.

Phagocytosis

Clip

Phagocytosis is when white blood cells “eat” a pathogen and release a chemical to destroy it.

Granulocytes

One class of leukocytes, called granulocytes, contain cytoplasmic granules and are produced in the bone marrow.

Eosinophils (parasites), basophils (allergies), and neutrophils (pus) are 3 types of granulocytes.

Some of these granulocytes are part of the third line of defense and others are part of the second line of defense.

Neutrophil Phagocytosis

AgranulocytesAgranulocytes do not have a granular cytoplasm, are

produced in the bone marrow but are modified in the lymph nodes.

Monocytes and lymphocytes are the 2 types of agranulocytes.

Monocytes turn into macrophages when they are released by the blood stream and perform phagocytosis.

Lymphocytes come in 2 forms: B Cells & T Cells. B Cells produce antibodies, and T Cells seek the intruder and organize the attack. Lymphocytes are part of the third line of defense.

http://www.youtube.com/watch?v=UKwwvIaR9aI

Development of Leukocytes

Inflammatory Response

Is triggered when tissue cells are injured by bacteria

Characterized by swelling, heat, redness, and pain.

Is a sign that a secondary defense is at work.

(a) Patient X. Indicators are reduced red and white blood cell counts.

(b) Patient Z. Indicators are higher body temperature and an elevated white blood cell count. The red blood cell count is normal.

(c) Patient Y. Indicators are increased white blood cell count and reduced red blood cell count because white blood cell growth in the bone marrow reduces the red blood cell count numbers.

Case Study

Hand out case study

Third Line of Defense- LymphocytesRemember lymphocytes can be B Cells or T Cells

Cell membranes of bacteria and outer coat of a virus contain antigens.

Antigens are any substance that triggers the formation of antibodies.

Third Line of Defense- Lymphocytes

Each cell in the human body has receptor sites that allow nutrients to enter.

Bacteria and viruses gain entry to the cell through these receptor sites.

Third Line of Defense- Lymphocytes

Each antibody is specific to the antigen that has invaded the body. For example: the antibody to fight strep throat will not fight a cold virus.

Note that antibodiesare Y shaped

How the BodyRecognizesAntigens

Helper T Cells are 1 type of T Cells

Remember our T Celllymphocytes and B Cell lymphocytes

Killer T Cells

Sometimes Killer T Cells (another type of T Cell) are needed to stop viruses.

Viruses can be evasive and can hide within the host cell. If this occurs, Killer T Cells are sent on a, “Search and Destroy,” mission.

The Killer T Cell will puncture the cell membrane of the host cell. This kills the body cell and the virus. It also prevents the virus from reproducing.

Suppressor T Cells and Memory T Cells

Once the battle between the invaders and the body is won, Suppressor T Cells (Yet another type of T Cell) signal the immune system to shut down.

Memory T Cells (Yes, a type of T Cell), store info about the antigen. If this antigen enters the body again, it will be defeated before they become established in the body.

Summary

Start with HIV intro questions

HIV

Human Immunodeficiency Virus

HIV is the virus that causes AIDS (Acquired Immune Deficiency Syndrome) .

HIV has an 8- 10 year incubation period before symptoms arise.

The immune system becomes weakened. A decrease in the function of CNS followed by bodyweight loss occurs.

Eventually death by a secondary infection such as pneumonia, meningitis, or fungal infection occurs.

Transmission of HIV

Through sexual intercourse, blood transfusion, injection with contaminated needle.

HIV infected mother through placenta and breast milk.

What Actually Happens?

HIV has a shape that provides access to the T Cell.

Unlike other viruses, the T Cell will engulf it.

If T Cells are attacked, explain in a journal entry how this weakens the immunesystem.

HIV Attacking Cells

http://www.youtube.com/watch?v=U2h0ECyMWhE

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter24/animation__hiv_replication.html

ELISA

ELISA test (Enzyme-Linked Immunosorbent Assay

Used to help detect diseases such as HIV

http://www.youtube.com/watch?v=RRbuz3VQ100

http://media.hhmi.org/biointeractive/vlabs/immunology/index.html