The Immune System and

The Lymphatic System Notes

 

Introduction:

The immune system is a defense system made up of an army of roaming white blood cells (WBC’s).  The battle between pathogen and WBC takes place mostly in the lymphatic system.

 

I. The Lymphatic System:

Functions:

1. Movement of body fluid through the body (maintaining homeostasis):  **When body fluid is in blood vessels it is called plasma, when fluid is in tissue it is called tissue fluid, and when in lymph vessels it is called lymph.
1. Plasma (fluid part of blood) is constantly diffusing out of the smaller blood vessels. (Carrys WBC, oxygen, and nutrients to the tissues.)
2. The tissue fluid then enters the lymph vessels. (Which run side by side with blood vessels.)
3. The fluid is carried up to the heart region where it is emptied back into the blood vessels.

 

2. Aids in the immune system=(WBC)-- High concentrations of WBC are found in the following components of the lymphatic system:
1. Lymph nodes: These are filter-like masses that contain WBC’s waiting to attack foreign pathogens.  When body fluid is carried through the lymph vessels it passes countless lymph nodes.
2. Tonsils: These are enlarged lymph nodes that trap pathogens that enter the nose and mouth. **If tonsils or lymph nodes are swollen or tender then this means that WBC’s are fighting pathogens.
3. Bone Marrow: (part of skeletal system) is the place where WBC’s are made.
4. Thymus: (part of the glandular system) is important gland where some WBC’s mature.  It is located above the heart.
5. Spleen: is a blood-filtering organ, which removes cellular debris and pathogens. 

 

II. THE IMMUNE SYSTEMà

A.  First Line of Defense à(Keep them out of the body!)

1.     The skin is the most important first line of defense. 

a.      Skin is part of another body system. (Integumentary System)

b.      The top layer of skin is composed of compact layers of dead cells that prevent pathogens from entering.

c.      Sweat and tears contain enzymes that prevent harmful bacterial growth.

2.      Mucus that lines the nose, throat, and lungs help trap pathogens.

3.      Pathogens and Mucus are then swept into the stomach, where acids destroy them.

 

 

 

B.  Second Line of Defenseà (Fight Localized Infections!)

1.     When a pathogen gets past the skin, invading body tissue, the cells react with an inflammatory response. 

a.      Chemical distress signals are released from the injured cells, causing the blood vessels to enlarge.  As a result, the skin will appear red at the point of injury/infection. 

b.       The expanded blood vessels leak out more fluid and WBC’s.   As a result, swelling occurs in the tissues surrounding the infection.

c.       The first WBC’s called to the scene are the macrophages. 

d.      Macrophage: a WBC responsible for cleaning up dead cells and pathogens.  They are nonspecific, meaning they treat every pathogen the same.  No matter what type of pathogen, they are all ingested and destroyed.

e.      Fever can be triggered by the macrophages.  Fever can be good at times, because higher temperatures kill many bacteria.  However, any fever over 103 degrees F. is considered dangerous to our bodies. 

 

C.  The Third Line of Defenseà (Fight Systematic Infections!)

1.      Some pathogens may slip by the macrophages and end up spreading through out the body.  When this happens, the other WBC’s come into action with an immune response.

 

a.      IMMUNITY – is the capacity of the human body to resist specific pathogens by identifying foreign antigens on them.

b.      An Antigen is anything that causes an immune response.

c.      Lymphocytes are types of WBC’s involved in immunity and the Immune Response. There are three types of lymphocytes:

i.        The Helper T cells, The B cells, and the Killer T cells.

ii.      These cells are capable of seeking out and destroying specific pathogens.

ii.       These are specific due to their ability to recognize foreign antigens or (markers) on pathogens. 

 

2.       How does the Immune Response work? 

a.  When a macrophage (the spy/intelligence) first ingests a pathogen, the macrophage sends out chemical signals to call Helper T cells (the general) to the site of infection.

b.       By the time these Helper T cells arrive, the macrophages have cleverly incorporated some of the foreign pathogen antigens onto it’s own cell membrane. 

c.  The helper T cell then attaches to the antigens on the macrophage and develops new binding sites that will recognize these foreign antigens.  (Helper T cells copy the enemy’s identification information)

d.      The helper T cell then passes on the enemies ID information to two different attack cells: the B cells and the Killer T cells. (types of soldiers)

 

 

3.      The B cells (the gun men) are responsible from making antibodies.  An antibody is a “Y” shaped protein that is released from the B cell and attaches to the pathogen.  Millions of B cells are cloned and millions of antibodies are released into the blood when fighting an infection.  Functions of antibodies:

a.      Antibodies can bind to pathogens marking them like flags so that macrophages know to destroy them. 

b.      Antibodies can also bind to viruses or bacteria toxins neutralizing their ability to harm us.

 

4.      The Killer T cells (hand-to-hand combat soldiers) Killer T cells will come into direct contact with a cell piercing a hole in it.  This hole allows water to rush in which causes the cell to burst.

a.       Killer T cells are produced at the same time as B cells. 

b.      They multiply in the lymph nodes and the thymus (they mature there) and then are released into the body fluids.

c.       Killer T cells are important in killing protists, virus-infected cells, and cancer cells.

d.       It is also responsible for rejection of organ transplants.

 

5.       Other WBC’s produced are the memory B and the memory T cells.  These are made after the first exposure to a specific pathogen.  These memory cells hang out in lymph nodes waiting.  If you are exposed or infected a second time by the same pathogen, memory cells quickly divide into B cells and Killer T cells.  The immune system can then respond quicker and with more punch. 

 

 

 

III. Problems involving the immune systemà

A.    An allergy is a disorder in which the immune system over-reacts to the presence of an antigen.

1.   Antigen examples include: pollen, mold spores, dust mites, and pet dandruff.

2.    Inflammatory response: Allergies trigger special cells called mast cells to release histamines, which produces symptoms such as sneezing, runny nose, and itchy eyes, and in some cases-asthma. 

3.    Asthma is an allergic reaction in which the smooth muscles in the lungs tightly squeeze the air passageways making breathing difficult.

 

B.   Autoimmune diseases occur when the immune system attacks its own body cells because the WBC’s no longer recognize “self” markers on certain cells.

1.   Examples and the cells they affect:  Grave’s disease (thyroid gland), multiple sclerosis (nerve cells), rheumatoid arthritis (joints), and Type “one” diabetes (insulin-producing cells).

 

C.   Rejection of Transplants:  donor organs are considered “non-self” and are attacked by the recipient’s immune system.  Rejection is prevented by closely matching the donor and recipients cell types.  Using certain drugs that suppress the recipient’s immune system also prevents rejection.

 

D.   Receiving Donated Blood:  The ABO blood group and Rh factor.  If the wrong blood type is given to a person, then the immune system will not recognize the blood and attack it.

 

 

E.   Cancer:   a condition in which the controls that stop cell growth do not work, causing the cell to multiply uncontrollably.  Cancer cells end up invading and destroying healthy tissue, which prevents the tissues of the body to function properly. 

 

1.      A tumor is a mass of cancerous cells.  Tumors can be classified as:

a.      Benign: A benign tumor does not spread to surrounding tissue. 

b.      Malignant: A malignant tumor spreads and destroys healthy tissue.

 

2.      Our immune system usually destroys cancer cells when they are produced in the body.  However, when the immune system fails to recognize these cancer cells, they end up growing into tumors.

 

3.       Some causes of cancer (all cause mutations)

a.      Viruses:

                                                                          i.      Virus examples that can cause cancer are: the herpes virus, the Epstein-Barr virus (mono), and the HPV virus (warts).

b.     Radiation:

                                                                          i.      Malignant Melanoma is a fatal skin cancer caused by ultraviolet radiation. (From the sun or tanning beds)

                                                                        ii.      Leukemia is a blood cancer caused by radioactive radiation.

c.      Chemicals:

                                                                          i.      Thirty percent of all cancers are caused by the carcinogenic chemicals in tobacco. (carcinogenic= cancer-causing)

 

 

4.      Cancer treatments:  includes surgery, localized radiation, and chemotherapy.

a.       In early stages of cancer:

i.      Surgery to remove a tumor could mean a complete cure.   (Early detection is critical for a successful recovery.)

b.     If cancer is not found early:

i.        Cancer spreads fast which means if not caught early, the tumor cells cannot always be removed completely.

ii.      Radiation is usually focused on the area in which the tumor has been removed to kill fast-growing cancer cells left behind.

iii.       Chemotherapy uses drugs that also kill fast-growing cancer cells.  It is used in combination with radiation.