Chapter 10

Blood and Immunity

SECTION 10-1 Blood

Functions of Blood (a liquid tissue)

1) to transport nutrients and oxygen to all the body cells when needed

2) to transport metabolic wastes and carbon dioxide from the body cells

3) to protect against blood loss (clotting)

4) to protect against invading organisms (immunity)

5) to regulate body temperature

6) to regulate pH and water levels in the blood



Components of Blood

1) Plasma is the liquid part of blood -> 55% of blood is plasma. About 90% of plasma is made up of water and the remaining 10% is made up of nutrients (amino acids, fatty acids, vitamins, sugars, minerals), enzymes, metabolic wastes, hormones, and plasma proteins.

3 Major Plasma Proteins

1) albumin- regulates the amount of water in the blood and body tissues by regulating the rate of osmosis to and from the blood and body tissues

2) fibrinogen - involved in blood clotting

3) globulin - helps to transport other substances through body e.g. antibodies

2) Cells

Red Blood Cells (erythrocytes)
White Blood Cells
(leukocytes)
carry oxygen and some carbon dioxide protect against disease
no nucleus, red in color and contain the protein hemoglobin nucleus, straw colored, no hemoglobin
30 trillion in body -> 5 million/ml 60 billion in body -> 7,000-10,000/ml
made in bone marrow -> 2 million/second made in bone marrow and lymph tissue -> 1 million/second
lifespan = 120 days lifespan = n/a
worn out rbc's are decomposed by liver and spleen n/a
remain in bloodstream have ability to leave circulatory system and will collect in areas of infection to attack invading organisms -> pus - dead wbc's, dead invading organisms, body fluid

Platelets are cell fragments formed from the cytoplasm of a type of cells (megakaryocytes) found in the bone marrow. The have no nucleus and are involved in blood clotting. They have a lifespan of 7 days and are produced at a rate of 200 billion per day.


Type of White Blood Cell

Function

neutrophils phagocytosis of small particles
monocytes phagocytosis of large particles
eosinophils release clot digesting enzyme -> plasmin

combat allergy causing substances

basophils release anti-coagulant to prevent spontaneous blood clots-> heparin

release histamine which causes inflammation

lymphocytes involved in immune response

White Blood Cell Tutorial

Blood Components

Blood Clotting

blood clotting - a process of enzyme catalyzed reactions in which blood solidifies to produce a plug at the site of an injured blood vessel

Steps of the Clotting Process

  1. A blood vessel ruptures which causes platelets in the blood to stick to the rough surface created by the rupture.
  2. The cells of the ruptured blood vessel and the platelets (which rupture as well) release the enzyme thromboplastin.
  3. Thromboplastin converts the inactive protein prothrombin to the active enzyme thrombin.
  4. Thrombin converts the soluble plasma protein fibrinogen to the insoluble fibrous protein fibrin.
  5. Fibrin sticks to the site of the blood vessel rupture and forms a mesh network to prevent further bleeding.
  6. After the damaged blood vessel has sufficiently healed, eosinophils release plasmin which will digest the blood clot.

Blood Clotting

Two Factors Which Prevent Blood Clots For No Reason

1) Platelets will only stick to rough surfaces and under normal circumstances (no ruptures) the inner wall of the blood vessel is extremely smooth.

2) Basophils release heparin which prevents blood clotting.

Clotting Problems

1) Vitamin K is needed to produce prothrombin. If vitamin K is lacking in the diet, only a small amount prothrombin is present and clotting may not occur as efficiently.

2) Hemophilia is hereditary disease in which one or more of the clotting factors is missing and clotting does not occur.

-> present in English Royal family

-> can bleed to death by simple nosebleed, bruising, menstruation

-> now treated with injections of missing components

Hemophilia

3) If the blood clot detaches before it is digested, it will flow through the blood stream and possibly get lodged somewhere in the circulatory system. This will prevent blood flow to tissue (embolism).

-> stuck in the brain -> cerebral embolism (stroke)

-> stuck in the lung -> pulmonary embolism

-> stuck in the coronary vessels -> coronary embolism (heart attack)

Stroke

SECTION 10-2 Immune System

A pathogen is any microorganism which can infect and possibly kill the infected organism. Pathogens include bacteria, viruses, and fungi. These organisms can be found in air, water, and food.

The immune system is the system of the body which prevents and resists the infection of pathogens.

Viral Infection

3 Lines of Defence

The 1st Line of Defence is a barrier system which prevents the pathogen from entering the body. There are 2 types of barriers:

physical barriers -> skin, nose and ear hair, mucus membranes, cilia of trachea, tears, sweat, saliva, urine

These physically stop the pathogens from entering the body.

chemical barriers -> stomach acid, sweat, tears, saliva

These have chemicals and enzymes which will destroy pathogen.

The 2nd Line of Defence is the inflammatory response due to the presence of pathogens attacking the cells of the body. As the body cells are under attack, body cells and basophils at the site release histamine which increases blood flow to the area and attracts phagocytes (neutrophils, monocytes, and macrophages). Macrophages are giant white blood cells which develop from monocytes and ingest large amounts of pathogens and damaged tissue. Due to the increased blood flow, the site of inflammation has certain symptoms such as redness, warmth, swelling, and pain (pinching of nerves).

Pus forms which consists of live and dead pathogens, dead white blood cells, and body fluid. The pus will drain from the body or be reabsorbed by the body.

If the pathogen is a virus, infected cells will release the protein interferon which will cause neighboring cells to create enzymes to prevent viral reproduction.

The 3rd Line of Defence is the immune response which uses the macrophages and lymphocytes to attack and destroy foreign material in the body. The system is based on the presence of antigens which are proteins or carbohydrates on the cell membranes of foreign cells. Antigens indicate to the immune system that these cells do not belong.

Cells Involved in the Immune Response: see page 204 fig. 10-9

Macrophages (monocytes)

Lymphocytes

T cells -> T-cells, helper T-cells, killer T-cells, memory T-cells, suppressor T-cells

B cells -> B-cells, plasma cells, memory B-cells

 

Functions of Each Cell Type

Macrophages ingest bacteria and viral infected cells and display the foreign antigens on its own cell membrane.

T-cells recognize the antigen on a virus or viral infected cell and is stimulated to divide by helper T-cell to form killer T-cells and memory T-cells.

Helper T-cells recognize the foreign antigen on the macrophage and stimulate the T-cells and B-cells to divide.

Killer T-cells have receptors on their cell membranes which will bind to the antigen on the viral infected cells and cause them to rupture.

Memory T-cells trigger the immune response by dividing into new killer T cells if the same foreign antigen is ever encountered again.

Suppressor T-cells shut down the killer T-cells and will slow down antibody production by plasma cells when the pathogens are brought under control.

B-cells recognize the antigens on bacteria and are stimulated by the helper T-cells to divide to form plasma cells and memory B-cells.

Plasma cells produce antibodies which will bind to the antigens and "mark them for death." This antibody-antigen complex signals for attack by phagocytes.

Memory B-cells will divide to form plasma cells to produce antibodies if the antigen (specific to the bacteria) ever return.

complement system - series of enzyme catalyzed reactions in the blood which cause the rupturing of bacterial cells

T-Cell Response

B-Cell (Humoral) Response

Types of Immunity

1) Active Immunity is a type of acquired immunity in which the body produces its own antibodies to attack a foreign antigen.

e.g. Having a viral or bacterial infection leads to the immune response which results the animal producing their own antibodies to the foreign pathogen.

Edward Jenner (1749-1823) "Father of Vaccination"
: He injected weakened forms of cowpox virus (non lethal) into people, and they made antibodies against it. Those antibodies also attached to the antigens of the smallpox virus (lethal) and caused it to be attacked by the immune system.

2) Passive Immunity is a type of immunity in which the body is given antibodies from the blood of another person or animal.

e.g. Maternal immunity occurs when antibodies from the mother are passed to the baby through the blood before birth and through the breast milk after birth. These protect the baby from infectious diseases for the first few months of life.

Vaccination

Antibiotics are not a form of immunity. They are a chemical substance produced by fungi or bacteria to fight off other pathogens. Researchers have isolated these substances to use to fight bacterial infections.

Blood Groups and Transfusions

There are 2 methods to group blood and both are based on the presence/absence of certain antigens on the red blood cells.

ABO Blood Grouping

Red blood cells have one, both, or neither of two types of proteins (antigens) on the outer surface...antigen A and/or antigen B. As well, a person is born with antibodies to fight foreign blood types...they will have the antibodies to fight whichever antigens their blood does not contain.

Blood

Type

% of

Population

(in USA)

Diagram Antigens

Present

Antibodies

in Blood

Blood Type Person Can Receive
A 40%



A anti-B antibodies A, O
B 12%

B anti-A antibodies B, O
AB 3%

A and B NONE A, B, AB, O
O 45%

NONE anti-A and anti-B antibodies O

transfusion - the process by which blood from one person is given to another

In order for a transfusion to be safe, the recipient should NOT have any antibodies to fight off the new blood.

ABO Antigens

Rh Factor

A second type of protein is also found on the surface of the red blood cell. It was first discovered on the rbc of the Rhesus monkey and thus named Rhesus factor, or RH factor. It was later seen on human rbcs. A person either has the protein, and is Rh+ (85% of the population) or does not have it, and is Rh- (15% of the population)

A person who is Rh+ can receive both Rh+ and Rh- blood in a transfusion, but a person who is Rh- can only receive Rh- blood because he/she will produce antibodies against the Rh protein.

RH Antigen

If a mother is Rh- and an unborn child is Rh+, there are problems. Normally, the blood cells between mother and baby do not mix, except during delivery when the placenta is torn away from the mother (afterbirth). When this happens, there is a chance that the blood will mix. This would cause the mother to produce antibodies against the baby's Rh+ blood. This is no problem because this baby has been safely delivered. However, the next child will receive these antibodies through the placenta, and its own immune system will attack its own blood...very bad!

To overcome this, when a mother who is Rh- and a father who is Rh+ have a child, she is given a needle several times during the pregnancy. The injection consists of RhoGAM, an antibody against any anti-Rh antibodies, so that they are destroyed.

Transplants

Organs and tissues can be transplanted from one individual to another. However, the recipient's immune system will often recognize the transplanted material as being foreign and will attack it (rejection) because it will have antigens present which are foreign to the recipient's immune system.

To prevent rejection during a transplant, two methods are used.

1) The donor and recipient should be related if possible, because they will share a number of antigens on their cells since they are related. (The more closely related, the better...for example, organ transplants from an identical twin are best; there is little chance of rejection. Transplants from a sibling are still good; from a cousin or other relative, the chances of rejection increase as you get farther apart on a family tree.)

2) Doctors will use of immune suppressing drugs, such as cyclosporine, which shuts down the immune system. Gradually the immune system regains strength and hopefully will not reject the transplanted tissue. Of course, this has the additional effect of increasing the chance of infection, because the immune system is also less able to fight off actual disease causing agents.

SECTION 10-3 Immune System Disorders

Acquired Immune Deficiency Syndrome (AIDS)

Aids is caused by the Human Immunodeficiency Virus (HIV) which specifically attacks the helper T cells of the immune system, thus shutting it down. The virus is transmitted primarily by sexual contact (semen/vaginal secretions) and blood to blood contact (intravenous drug use -> sharing needles; transfusions; mother to fetus). Prevention strategies include 1) abstinence, 2) latex condoms, 3) avoiding drug use/abuse 4) careful screening at blood donor clinics.

The individual does not die due to presence of HIV, in fact it may be many years before the disease AIDS even develops, because the virus remains dormant. Also, AIDS itself does not actually kill the victim directly...death is often due to infectious disease or cancer (normally the immune system will filter and destroy cancer cells) that the body is unable to fight off due to the weakened immune system. A rare form of cancer which is prevalent in AIDS victims is to Kaposi's Sarcoma. This is a cancer of the blood vessels. Another disease prevalent among AIDS victims is a type of pneumonia caused by Pneumocystis carinii.

Allergies

An allergy is a disorder due to the rapid over-reaction of the immune system to an antigen which is normally not harmful. ( e.g. insect bites, nuts, flower pollen)

The reaction causes the release of histamine which results in the inflammatory response (redness, swelling, hives, increased mucus secretions). Allergies are often counteracted by antihistamine.

Allergy Movie

Autoimmune Disorders

These are a group of disorders in which the body's immune system treats parts of the body as being foreign.

examples include:

juvenile diabetes - The immune system attacks the beta cells of the pancreas which produce insulin, rendering the individual a Type 1 diabetic.

rheumatoid arthritis - The immune system attacks the joints of the body causing inflammation.

multiple sclerosis - The immune system attacks the fatty substance (myelin) around nerve cells, disrupting the function of the nerve cells

lupus erythematosus - The immune system attacks the connective tissue of different parts of the body.

rheumatic fever - A bacterial infection which causes the immune system to attack joint and heart tissue (often valves which results in scar tissue and a heart murmur).

Cancer

Cancer is due to the uncontrolled growth of the cells of the body. Cancer cells do not function normally, and are likely produced at all times during our life, but are kept in check by immune system. A weakened immune system may allow these cells to grow and spread through the body.

Leukemia is a form of cancer that affects the blood cells, specifically the leukocytes (white blood cells).