Hemoglobin (Hgb) Measures the Amount of Oxygen-Carrying Protein in the Blood
Immunity
Red blood cell (RBC) count is a count of the actual number of red blood cells per volume of blood. Both increases and decreases can point to abnormal conditions.
Hemoglobin (Hgb) measures the amount of oxygen-carrying protein in the blood.
Hematocrit (Hct) the ratio of packed red blood cells to total blood volume. Normal is about 45%
Thalassemia A hereditary form of anemia where the RBCs have abnormal hemoglobin that deforms the cells into strange shapes (target cells, teardrops, spheres)
Sickle Cell Disease
A hereditary mutation resulting in one valine amino acid substituted for glutamic acid.
Present in African Americans more than in other groups, and is always characterized by sickled erythrocytes.
The sickle shape helps prevent malaria infections, but it also causes blood clots.
Pernicious anemia (megaloblastic anemia)
Very large erythrocytes, caused by lack of vitamin B12 or intrinsic factor
When a person has gastric bypass surgery, the stomach is no longer able to produce intrinsic factor, which is needed to absorb vitamin B12, which is needed to make hemoglobin in RBC’s.
Without this vitamin, the blood cells are fewer and much larger than normal (megaloblastic).
The surgery patient must take vitamin B12 shots or sublingual supplements for the rest of their life.
LEUKEMIA
Cancer of the blood is called leukemia. It actually only involves the white blood cells.
Something goes wrong in one stem cell, and it starts making huge amounts of clones of itself which don’t work right and not enough normal white blood cells are made. Therefore, the body cannot fight infection. So, the immature white cells are sent into the bloodstream. It’s better to send a young cell with no weapons to the war than to send nothing at all!
Think of Leukemia as too few mature white blood cells.
Even though the WBC count is high, they are all immature forms.
Disorders of Platelets
– Thrombocytopenia
- Abnormally low concentration of platelets
- Blood does not clot properly
Pathogen“Path” = disease “ogen” = generating
A pathogen is something that causes disease.
A biological pathogen is a bacterium, virus, fungi, yeast, protozoa, worms, etc.
A non-biological pathogen can be a toxic chemical, asbestos, etc.
Usually, the term “pathogen” refers to a biological pathogen.
Sizes of Pathogens
Bacteria are so small that hundreds of them can fit inside one white blood cell.
However, bacteria usually do not invade body cells. They live between the cells of the body, using up nutrients in the area, and they cause harm by secreting toxins.
Viruses are so small that thousands of them can fit inside the NUCLEUS of one white blood cell.
They always try to invade body cells because they need a piece of our DNA or RNA in order to replicate.
When a body cell has been invaded by a virus, the entire cell must be killed by a white blood cell.
Antigen
An antigen is anything that causes an immune response, which isn't necessarily a biological pathogen (disease-causing organism).
A non-biological antigen can be pollen, dust, grass, or anything that a person is allergic to.
Pollen can be an antigen to a person with allergies, but it is not an antigen to a person without allergies, because no immune response was launched.
LEUKOCYTES (White blood cells)all fight infection
BASOPHILS
◦ MAST CELL
EOSINOPHILS
NEUTROPHILS
MONOCYTES
◦ MACROPHAGES
LYMPHOCYTES
◦ B CELLS
◦ T CELLS
BASOPHILS
◦ Basophils – only about 0.5% of all leukocytes
▪ Granules secrete histamines (vasodilation; more WBCs can get to the infection site)
▪ Antihistamines interfere with the function of basophils.
▪ Mast Cell: a basophil that leaves the blood vessel and enters the tissues.
Eosinophils
Eosinophils – compose 1-4% of all WBCs
◦ Play roles in:
▪ Ending allergic reactions, parasitic infections
▪ During these conditions they increase in numbers: eosinophilia
▪ (too many is ___philia
▪ too few is ___penia)
Neutrophils
Neutrophils – most numerous WBC
First to respond to infection
◦ Phagocytize and destroy bacteria
◦ Also destroy bacterial toxins in body fluids
◦ Nucleus – has two to six lobes
Neutrophils are the white blood cells that contribute to immunity mainly by engulfing BACTERIA and foreign bodies (thorns, dirt, etc) in a process called phagocytosis.
They release the contents of their lysosomes onto the invader, dissolving it.
When a bacterium has a capsule, it makes it hard to phagocytize, so the neutrophil requires opsonization by antibodies.
Opsonization
Some bacteria have evolved a slippery capsule around them as a defense against phagocytosis. The neutrophil cannot engulf this type of bacteria. Neither can a macrophage.
When an antibody attaches to this type of bacteria, the neutrophil can now grab onto the antibody like a handle, enabling it to phagocytize the bacteria.
This process of facilitation of phagocytosis is called opsonization.
When an invading bacteria has the antibody attached to its cell membrane, the entire structure is now called an antigen-antibody complex.
If a bacterium does not have a capsule, the neutrophil can destroy it without opsonization. The antibody can also destroy the bacterium by itself by popping the cell membrane.
But when a capsule is present, the neutrophil and antibody work best together.
Neutrophils are also the ones that primarily destroy the dissolved toxins that bacteria secrete into body fluids.
Monocytes
Comprise about 5% of all WBC’s.
Like neutrophils, they phagocytize (eat) bacteria, old cells, and foreign bodies. They have more types of lysosome enzymes than neutrophils so they are better at killing difficult pathogens.
They also use antibodies for opsonization.
When they leave the bloodstream and enter the tissues, they are called MACROPHAGES.
What’s the Difference between Neutrophils and Monocytes/Macrophages?
There are 10x more neutrophils in the bloodstream than monocytes/Macrophages. Consider neutrophils to be the most numerous white blood cell.
However, there are more macrophages in the tissues of the body. They are everywhere!
Neutrophils live only a few days. Monocytes/Macrophages live a few months. Lymphocytes live for years.
Monocytes/Macrophages are larger and slower than neutrophils, but they can phagocytize larger organisms and more of them.
Neutrophils usually just phagocytize bacteria until they die. Macrophages phagocytize and then take pieces of the dead bacteria and present them to lymphocytes so a larger immune response can occur.
Differences in Function
There are two types of phagocytes: Neutrophils and macrophages.
◦ Neutrophils and macrophages both mainly function by phagocytizing bacteria (not viruses).
Lymphocytes are mostly needed to kill off body cells infected by viruses.
Neutrophils just phagocytize bacteria and secrete chemicals to recruit more white blood cells to the site.
Unlike neutrophils, macrophages have surface receptors; these "recognize" the surface of the pathogen’s cell membrane.
Macrophages phagocytize the bacteria, pop their lysosomes onto it, and dissolve it, except for some pieces of the bacteria’s cell membrane.
The macrophage places these pieces of bacteria on its own cell membrane, and finds a lymphocyte to present it to.
Macrophages present these pieces to T cell lymphocytes and to B cells lymphocytes.
The lymphocyte feels the shape of the bacteria pieces on top of the macrophage, (this is called “antigen presentation”) and the lymphocyte can then launch an attack on the rest of the bacteria still alive in the body.
In this way, the macrophage recruits even more lymphocytes to join the war.
So, what is a lymphocyte?
Lymphocytes
20–45% of WBCs
◦ The most important cells of the immune system
◦ There are two types of lymphocytes; one type is effective in fighting infectious organisms like body cells infected with viruses
◦ Both types of lymphocytes act against a specific foreign molecule (antigen)
Two main classes of lymphocyte
B cells – Originate in the bone marrow, mature into plasma cells. A mature plasma cell fights infection by producing antibodies
◦ B cells – mature into plasma cells
◦ Plasma cells secrete antibodies; the plasma cell’s antibodies are what kills the attacking cell.
◦ Antibodies attack in two ways:
◦ They attach to bacteria and pop the cell membrane
◦ They attach to encapsulated bacteria to help neutrophils and macrophages to phagocytize them.
◦ Disorder of B-cell Lymphocytes
▪ Mononucleosis: Epstein Barr virus attacks B lymphocytes. It is characterized by inflammation of lymph vessels (lymphangitis).
Lymphangitis: lymph vessel inflammation; usually from infection.
◦ Infected lymphocytes have a characteristic scalloped edge where they touch RBC’s
Function of a B Lymphocyte
T cells – Originate in the thymus gland. They attack foreign cells directly (including organ transplants!). They can also kill viruses.
◦ T cells – coordinate the immune response by recruiting other white blood cells.
◦ They can directly destroy bacteria by popping their cell membrane.
◦ T cells can also directly destroy foreign cells by popping the cell membrane.
◦ They do not need to phagocytize the invading cell. They do not need the assistance of antibodies.
◦ T-cells can therefore kill a body cell that has become infected with viruses.
◦ T cells are the cells that attack organ transplants!
▪ Immunosuppression drugs are designed to inhibit the action of T cells.
▪ T cells are attacked by the HIV (AIDS) virus.
▪ The thymus gland secrets certain hormones which can cause T cells to become immunocompetent (makes the cells mature and start to work)
There are several types of T cells. The main types are:
Cytotoxic (Killer) T cells
◦ Go out and directly kill bacteria or infected host cells
Helper T cells
◦ Release chemicals called “cytokines” to call in more white blood cells of all types to join in the war. They also present the macrophage’s antigen to a B cell, which causes it to produce antibodies against that particular bacteria. The B cell is now called a plasma cell
Suppressor T cells
◦ Stop the immune process when it is over, and also "tell" some plasma cells to "remember" how to destroy that specific pathogen. Those plasma B-cells are then called Memory B-Cells. They can react to the same pathogen faster, the next time it invades because Memory B-cells already have the proper antibodies stored up for that pathogen.
Function of a T- Lymphocyte
Summary
A pathogen somehow gets past the body's physical and chemical barriers and the inflammation response.
The pathogen is engulfed by a macrophage (or neutrophil).
The macrophage releases the contents of its lysosomes onto the bacterium and dissolves most of it. There are still some pieces of the bacterium’s cell membrane left. The macrophage then forces the surface proteins of the bacterium (antigens) to it's own cell surface.
Helper T-Cells touch these surface antigens, make a copy of their shape, and present them to B-cells to make antibodies against them.
These Helper T-Cells begin to multiply and have two main roles.
The first is to activate B-Cells and "tell" them how to neutralize the pathogen by presenting the pieces of the bacterium cell membrane so the B-cells can make antibodies.
◦ The B-Cells (now called Plasma cells because they have been activated) begin to multiply and produce the antibodies to neutralize this specific pathogen.
The second role of Helper T-Cells is to activate the Killer T-Cells.
Killer T-Cells can either destroy the pathogen itself (bacteria), or destroy the entire body cell which is infected (viruses).
When the immune response is over, Suppressor T-Cells stop the process and also "tell" some B-Cells to "remember" how to destroy that specific pathogen. Those B-cells now become Memory B-Cells.
Antibodies
The small region at the tip of the protein is extremely variable, allowing millions of antibodies with slightly different tip structures, or antigen binding sites, to exist.
This region is known as the hypervariable region. Each of these variants can bind to a different target, known as an antigen.
This huge diversity of antibodies allows the immune system to recognize an equally wide diversity of antigens.
Some of these “Y” shaped units exist by themselves (monomers)
Some are in pairs (dimers)
Some are in a cluster of five (pentamers)
There are five different antibody types , which perform different roles, and help direct the appropriate immune response for each different type of foreign object they encounter.
Types of Antibodies
- IgD – initiation of immune response
- IgE – stimulates allergic reactions, good for
- worm infections
- IgG – highest concentration in blood, highest
- amounts in most secondary responses,
- crosses the placenta
- IgA – secretory Ig, found in secretions,
- highest concentration in body
- IgM – produced first, best at C’ activation
IMMUNITY
Most people are sick more often as children than as adults in their 20s through 30s because we build up many varieties of memory lymphocytes during childhood, providing immunity from more and more antigens during adulthood.
Myasthenia gravis
Myasthenia gravis (MG): autoimmune disease where antibodies destroy or block receptors for acetylcholine, a neurotransmitter.
Causes muscle paralysis.
First attacks small muscles especially those that keep eyes open; will spread to diaphragm death.
To stave off effects, do thymectomy.
Aspirin
One baby aspirin a day can help prevent blood clots.
It blocks the ability of an enzyme called COX (cyclo-oxidase) to cleave arachidonic acid into a molecule called a prostaglandin.
Prostaglandins are needed for inflammatory reactions and for making clotting factors.
COX inhibitors, such as aspirin, block pain from inflammation, but they also INCREASE blood clotting time.
Life span, from longest-lived to shortest-lived:
Lymphocytes
Erythrocytes
Platelets
Neutrophils
Terms
- Excess neutrophils: neutrophilia
- Few neutrophils: neutropenia
- Excess platelets: thrombocytophilia
- Few platelets: thrombocytopenia
WBC Count
White blood cell (WBC) count is a count of the actual number of white blood cells per volume of blood. Both increases and decreases can be significant.
White blood cell differential looks at the types of white blood cells present. There are five different types of white blood cells, each with its own function in protecting us from infection. The differential classifies a person's white blood cells into each type: neutrophils (also known as segs, PMNs, granulocytes, grans), lymphocytes, monocytes, eosinophils, and basophils.
BLOOD TYPING: The ABO SYSTEM
Blood typing is the technique for determining which specific protein type is present on RBCs.
Only certain types of blood transfusions are safe because the outer membranes of the red blood cells carry certain types of proteins that another person’s body will think is a foreign body and reject it.
If a person with type A blood gets a transfusion of type B antigens (from Type B or Type AB, the donated blood will clump in masses (coagulation), and the person will die.
The same is true for a type B person getting type A or AB blood.
Type O- blood is called the universal donor, because there are no antigens, so that blood can be donated to anyone.
Type AB+ blood is considered the universal acceptor, because they can use any other type of blood. This blood type is fairly rare.
The rarest blood type is AB negative.
RH FACTOR
There is another term that follows the blood type. The term is “positive” or “negative”. This refers to the presence of another type of protein, called the Rh factor. A person with type B blood and has the Rh factor is called B positive.
A person with type B blood and no Rh factor is called B negative.
The reason this is so important is that if an Rh- mother has an Rh+ fetus in her womb (from an Rh+ father), her antibodies will attack the red blood cells of the fetus because her body detects the Rh protein on the baby’s red blood cells and thinks they are foreign objects. This is called Hemolytic Disease of the Newborn (HDN).
HDN
This can be prevented if the doctor knows the mother is Rh- and the father is Rh+, because that means the baby has a 50% chance of being Rh+ like the father.
Therefore, anytime a mother is Rh-, even if the mother says the father is Rh-, you can’t be sure who the father is, so they will proceed as though the baby may be Rh +.
They will give her an injection of a medicine (Rhogam) that will prevent her immune system from attacking the baby.
Rhogam
Rhogam is given at 18 weeks into the pregnancy and again within 72 hours after giving birth.
It is usually given within 2 hours after giving birth since you can’t trust the patient to return after they leave the hospital.
The first baby is not at risk; during the first birth (or miscarriage), the placenta tears away and that’s when the baby’s blood cells get into the mother’s bloodstream.
She then forms antibodies against the Rh factor, which are ready to attack the second fetus.
The baby does not make the Rh factor until about 18 weeks into the pregnancy.
IMMUNE SYSTEM
INFLAMMATORY REACTION: When you get stuck by a thorn or have an infected cut, the body goes through a series of events called an inflammatory reaction.
Four outward signs:
Redness (erythema or rubor)
Heat (calor)
Swelling (edema)
Pain (dolor)
INFLAMMATORY REACTION
Redness is caused from the blood vessels dilating to allow more blood flow to the area. Within the blood are platelets to clot the blood, proteins to repair the damage, and macrophages, which are white blood cells that eat up the foreign body, bacteria, or the dead cells.
Heat is caused because of the extra amount of warm blood flow to the area.
Swelling is caused from the plasma that leaks out of the swollen blood vessels.