Figure 14.1

Immunology: the study of all features of the body’s second and third lines of defense

Healthy functioning immune system is responsible for:◦ Surveillance of the body◦ Recognition of foreign material◦ Destruction of entities deemed to be foreign

White blood cells must distinguish self from nonself cells

Evaluates cells by examining markers on their surfaces

Figure 14.4

White blood cells

◦ B lymphocytes◦ T lymphocytes

Anything that is foreign to the

body (non self) and will elicit an immune response.

ie. an infectious agent

A group of serum proteins whose function is to attack and inactivate non-selfentities.

Two types of Immune Responses

Cell Mediated

Humoral

Figure 15.4

The cells and cell fragments in plasma are called formed elements

Three types of formed elements Erythrocytes – carry

oxygen and carbon dioxide in the blood

Platelets – involved in blood clotting

Leukocytes – involved in defending the body against invaders Divided into

granulocytes and agranulocytes

T lymphocytes

There are a variety of different immune cells whose functions are to recognize, tag/label, and inactivate non-self:

◦ T helper◦ T cytolytic◦ T suppressor

The most important component of the immune system is the T helper cells.

They wander around body as sentinels, looking for things that aren’t supposed to be there.

When they find something they alert the cytolytic cells to destroy.  

 T lymphocytes (cell

mediated)

T-helper (recognition) T-cytolytic (inactivation) T-supressor (regulation and

modification of cell mediated immune response)

 

Granulocytes Contain large granules

that stain different colors based on the dye used

Three types Basophils – stain blue

with the basic dye methylene blue

Eosinophils – stain red/orange with the acidic dye eosin

Neutrophils – stain lilac with a mixture of acidic and basic dyes

Granulocytes

Neutrophils and eosinophils can phagocytize pathogens

Neutrophils and eosinophils are capable of diapedesis

◦ Defensive blood cells: leukocytes Lab analysis of

leukocytes The differential white

blood cell count test can signal signs of disease Increased eosinophils

can indicate allergies or parasitic worm infection

Bacterial diseases often show increase in leukocytes and in neutrophils

Viral infections show increase in lymphocytes

◦ Can be divided into five stages Chemotaxis Adherence Ingestion Killing Elimination

Killing by eosinophilsMainly attack parasitic helminths (worms) by attaching to their surfaceSecrete toxins that weaken or kill the helminth

Eosinophilia, or elevated eosinophil levels, is often indicative of a helminth infestation

◦ Killing by neutrophils Produce chemicals that

kill nearby invaders Generate extracellular

fibers called neutrophil extracellular traps (NETs) that bind to and kill bacteria

[INSERT FIGURE: 15.7]

Complement Activation of complement

Body’s own cells withstand complement cascade Membrane-bound

proteins on many cells bind with and break down activated complement proteins

[INSERT FIGURE: 15.11]

• Set of genes that codes for human cell receptors

• Gives rise to a series of glycoproteins (MHC molecules) found on all cells except red blood cells– Class I genes- code for

markers that display unique characteristics of self

Cytokines are critical to the development and functioning of both the innate and adaptive immune response, although not limited to just the immune system.

They are often secreted by immune cells that have encountered a pathogen, thereby activating and recruiting further immune cells to increase the system's response to the pathogen.

Role of Beta lymphocytes

Formed in response to a foreign entity in thebody. Antibodies formed against toxins, bacteria, viruses, and fungi.

Beta lymphocytes produce/secrete plasma cells which make immunoglobulinsaka – antibodies

5 different classes of antibodies◦ Ig μ – Mu◦ Ig G - Gamma◦ Ig E – Epsilon◦ Ig A – Alpha◦ Ig D – Delta

Structure is normally pentameric.

This is considered to be the largest of all the antibody molecules and accounts for about 5-10% of the immunoglobulin pool. Located in the blood, lymph, and on B cell surfaces, these are the first antibodies to be produced in the first few days of a primary immune response to an infecting organism. IgM antibodies are effective against microbes and agglutinating antigens. As a consequence of its structure, IgM is also a good agglutinator (combiner) and can clump microorganisms together for eventual elimination from the body. Microbiology and Immunology Online.

http://pathmicro.med.sc.edu/mayer/IgStruct2000.htm (Accessed on July 22, 2007)

IgG (structure is monomeric)

IgG is the smallest and most predominant immunoglobulin of internal components such as blood, cerebrospinal fluid, and peritoneal fluid. IgG makes up 80% of the total immunoglobulins and is considered the most versatile due to its capacity for carrying out the same functions as other immunoglobulin molecules.

IgG is the only class of immunoglobulin that crosses the placenta conferring the mother's immunity on the fetus.

Capable of diffusing into the interstitial fluid due to its very small molecular weight, it enhances phagocytosis, neutralizes toxins and viruses, and protects the fetus and newborn

IgA (structure can be mono- or dimeric)

IgA represents 10 to 15% of the total circulatory immunoglobulin pool. IgA predominates in body secretions and is mainly concerned with defending the exposed external surfaces of the body.

It is found in the secretions of saliva, tears, nasal fluids, colostrums breast milk, sweat, genito-urinary and gastro-intestinal tracts, secretions of the lungs, etc. IgA plays an important role in protection against respiratory, urinary tract and bowel infections and it is probably also

importantin preventing absorption of potential antigens in the food we eat.

Its significant presence in colostrum and breast milk indicates that it can be transferred across the gut mucosa in the neonate and plays an important role

in protecting the neonate from infection.

IgD (structure is monomeric)

IgD is primarily a cell membrane immunoglobulin found on thesurface of B lymphocytes and accounts for less than 1% of the total immunoglobulin pool.

While their serum function is not fully understood, they are known to initiate immune response on the B-cell surface (is expressed on B cells as an antigen receptor).

IgD antibodies are found in small amounts in the tissues that line the belly or chest.

IgE (structure is monomeric)

Athough difficult to find (constituting about .002% of immunoglobulins), IgE antibodies are

of major importance as mediators of allergic reactions and are also generally responsible

for an individual's immunity to invading parasites.

IgE antibodies are found in the lungs, skin, and mucous membranes. They cause the body

to react against foreign substances such as pollen, fungus spores, and animal dander by

triggering the mast cells to release histamine along with a variety of other mediators that

result in allergic symptoms such as increased vascular permeability, skin rashes,

respiratory tract constriction (wheezing), and increased secretions from epithelium (watery

eyes, runny nose).

This may occur in allergic reactions to milk, some medicines, and some poisons. Thus,

IgE antibody levels are often high in people with allergies.

 

IgE also plays a role in parasitic helminth diseases. Since serum IgE levels rise in parasitic

diseases, measuring IgE levels is helpful in diagnosing parasitic infections.

Figure 15.15

Figure 15.13