Immune System

Standards:

SAP 1 – Students will analyze anatomical structures in relationship to their physiological functions.

SAP 4 – Students will analyze the physical, chemical, and biological properties of process systems as these relate to transportation, absorption, and excretion, including the cardiovascular, respiratory, digestive, excretory, and immune systems.

Pathogens are disease causing organisms

examples: bacteria, viruses, fungi and protists

The body has 3 main lines of defense to prevent invading microbes from getting the upper hand

First line of defense

Made up of the skin and mucous membranes

• skin covers the outside of the body

• mucous membranes line the body’s internal surfaces (digestive tract, nasal passages, respiratory passages, and reproductive tract)

Together, the skin and mucous membranes function to prevent microbes from entering the body

• when pathogens penetrate the 1st line of defense (through cuts or wounds), the 2nd line of defense comes into play

Second line of defense

Made up of:1. Three types of cells that kill

invading microbes

a. Macrophages are WBCs that travel through the body to kill invading bacteria by ingesting them

b. Neutrophils are WBCs that release chemicals that kill invading bacteria and themselves in the process

c. Natural killer cells are defense cells that kill any body cell that has become infected with a virus

• more importantly, natural killer cells are our best defense against cancer

• they detect and kill cancer cells before they can form tumors

2. Complement – is a group of proteins that circulate in your bloodstream

• they function to kill invading bacteria and fungi

3. The inflammatory response is to series of events that functions to suppress infection and speed healing

• it occurs anytime you have been injured

A series of events occur during an inflammatory response

1. Damage cells release alarm chemical that

2. Attract neutrophils and macrophages to the damaged area which

3. Cause local blood vessels to dilate increasing blood supply to the damaged area

• This is what causes the four classical symptoms of inflammation (heat, redness, pain, and swelling)

The cardinal signs of inflammation are rubor (redness), calor (heat), tumor (swelling), dolor (pain), and loss of function.

4. Temperature response – activated macrophages (those consuming invading bacteria) send signals to the brain to increase your body temperature above normal (98.6F / 37C)

Low grade temperatures (less than 103F/ 39C) speed the healing process because they inhibit the growth of bacteria

However, high grade temperatures (greater than 105 F/ 41C) are often fatal because they destroy important enzymes in the body

Third line of defense

Made up of your immune system

It functions to combat major invasions, and comes into play only when your first 2 lines of defense have failed to kill the invading pathogens

1. Key players in the immune system

a. Macrophages – WBCs that initiate the immune response

• they release an alarm signal that functions to activate Helper T cells

b. Helper T cells – WBCs that function to activate Killer T cells and B cells

c. Killer T cells – WBCs that recognize and kill body cells infected with a virus

d. B cells – WBCs that produce antibodies that mark pathogens for destruction by macrophages and natural killer cells

• some of these activated B cells will become memory cells that remain in your body for a long time – sometimes for life

These memory B cells are programmed to recognize the same pathogen that they encountered earlier in you life

If they ever encounter that same pathogen again, they rapidly produce large amounts of antibodies that destroy the pathogen before they have a chance to cause the disease a second time

2. Vaccination – prevent disease by tricking your immune system into thinking your body has been invaded by a particular pathogen

The vaccine you receive usually contains a dead or disabled pathogen which cannot cause disease, but does result in the formation of memory B cells that patrol the body preventing future infections by the same pathogen

Vaccinations exists for many diseases: polio, tetanus, diphtheria, measles, and smallpox

Polio

Tetnus

Diphtheria

Diphtheria

Measles

Measles

Smallpox

Smallpox

Smallpox

Smallpox vs. Chickenpox

• smallpox vaccinations are no longer required because this disease has been eradicated from the earth

Malfunctions and Failures of the Immune System

1. Autoimmune diseases – diseases in which the body attacks its own cells

• we do not know what triggers the development of these diseases

There are several different types of autoimmune diseases:

a. Multiple sclerosis occurs when the immune system attacks and slowly destroys the myelin sheath that surrounds and protects your nerves

As the myelin is destroyed, your nerves lose their ability to conduct impulses

This results in progressively worsening paralysis and eventually death

• there is no cure

b. Systemic lupus erythematosus – occurs when the immune system attacks and destroys your connective tissue, joints, and kidneys

Eventually causes death

• there is no cure

c. Type 1 diabetes – occurs when the immune system destroys insulin-producing cells in the pancreas

• there is no cure, but can be controlled by taking daily insulin injections

d. Rheumatoid arthritis – occurs when the immune system attacks and destroys cartilage in your joints

As the cartilage is destroyed, bone begins rubbing against bone causing tremendous pain

• there is no cure

2. Allergies – occur when the immune system mounts a major attack against a normally harmless substance

For example, if you are allergic to pollen, your immune system treats the pollen as if it were a pathogen, causing nasal congestion and a runny nose

3. SCID (severe combined immunodeficiency) – a rare disease in which a person is born with missing or inactive B cells and T cells

This person has no immune system. Thus, they could be killed by a cold virus

The most famous patient with SCID was David, the “bubble boy”, who lived in a sterile plastic bubble for almost all of his life; he died in 1984 at the age of 12

4. AIDS (acquired immune deficiency syndrome) – disease caused by HIV (human immunodeficiency virus)

Although AIDS was first recognized as a disease in 1981, it has been around since 1959

HIV is transmitted by:

1. Sexual intercourse with an infected person

2. Sharing hypodermic needles with an infected person (IV drug use)

3. Receiving blood transfusions or blood products (factor VIII used by hemophiliacs) from an infected individual

HIV is not transmitted through air, on toilet seats, by shaking hands or sharing food or drink

There is no cure. HIV transmission can be prevented by not sharing hypodermic needles and abstinence.

Condoms can help prevent HIV transmission, but there is no guarantee

In 1989, it was discovered from tissue samples that a British sailor died of AIDS in 1959

HIV causes death by attacking helper T cells. As a result killer T cells and B cells cannot be activated. Thus, the body is susceptible to infections and cancer

HIV infected individuals are considered to have AIDS when their helper T cell count falls below 200/mL

(normal is 800 – 1000/mL)

Diseases that commonly cause death in AIDS patients are:

Pneumocystis pneumonia

Kaposi’s sarcoma (cancer of skin and mucous membranes)