CHOOSE HAPPINESS!

“ The basic thing is that everyone wants happiness, no one wants suffering; And happiness mainly comes

from our own attitude rather than external factors. If your own mental attitude is correct, even if you remain

in a hostile environment, you feel happy.”-Tenzin Gyatso, 14th Dalai Lama

THE IMMUNE SYSTEM“System of defense against pathogens”

Please refer to pages 1-5 of your Common Diseases of Companion Animals book and pages

242-246 in your Clinical Anatomy and Physiology book

Immunology

• Immunity

– The ability of the body to fight infection and/or foreign invaders by producing antibodies or killing infected cells.

• DIVIDED INTO 2 LARGE CATEGORIES: NONSPECIFIC AND SPECIFIC IMMUNITY

• Immune System

– The system in the body responsible for maintaining homeostasis by recognizing harmful from non-harmful organisms and producing an appropriate response.

Foreign Invaders

• Called Pathogens– Viruses, bacteria or other

living thing that causes disease/immune response.

• Antigens– Soluble substances:

Toxins & foreign proteins

– Particulate: Bacteria/ tissue cell

Parts of the Immune System

1. Blood - White Blood Cells in particular2. Bone Marrow – Produces B Lymphocytes and

T lymphocytes3. Thymus Gland – consist of T Lymphocytes

(originally produced in the bone marrow)– Recognizes self from non-self– Mature and than move to spleen lymph nodes

looking for invaders

4. Normal functioning: nutrition, stress, sanitation and age

Nonspecific vs. Specific

IMMUNOLOGY : NON-SPECIFIC IMMUNITY

• NONSPECIFIC IMMUNITY - INCUDES SPECIES RESISTANCE, MECHANICAL/CHEMICAL BARRIERS, AND INFLAMMATION

First Line of Defense – The Skin• Provides Physical/mechanical and Chemical barriers

• Physical – hard to penetrate, made of indigestible keratin, hairs

• Chemical – tears, sweat, mucous, saliva , enzymes, sebum

Second Line of Defense – Inflammatory Response –When foreign invaders gain access to the body

• SIGNS OF INFLAMMATION:REDNESSHEATPAINSWELLING

*cells of the invaded tissue release enzymes called mediators that attract white blood cells via chemotaxis. Blood vessels dilate and become more permeable. Specific white blood cells, usually neutrophils, begin to “gobble up” the foreign material (phagocytosis).

IMMUNOLOGY: NON-SPECIFIC IMMUNITY

Nonspecific Immunity

• Inteferon– Substance that prevents

replication of virus in the host cell

• Complement– Group of enzymes

activated by specific & nonspecific immune system

– Act on cell wall > pores in membranes > rupture/lysis of the cell

IMMUNOLOGY: SPECIFIC IMMUNE RESPONSE

Third Line of Defense – Specific Immune Response – Conducted by 2 types of white blood cells called lymphocytes (B-cell And T –

cell lymphoctyes)

IMMUNOLOGY: SPECIFIC IMMUNE RESPONSE

This is a specific response to a specific pathogen/antigen.• B-cell lymphocytes are responsible for humoral immunity,

which involves the creation of Antibodies.– Clone of cells some plasma cells > Ab and others become memory

cells– Long time to respond– Memory cells and Ag is presented again than it is shorter

• T-cell lymphocytes carry out cell-mediated immunity by directly combining with the foreign cell and destroying it or rendering it incapable of causing disease– Macrophages help present antigen – antigen presenting cells– Faster response

The Pathway of Specific Immune Response

Pathogens

Pathogens eaten by Macrophage

Displays portion of Pathogen on surface to T cells

Helper-T cell recognizes Pathogen

Step 1

Step 2

Step 3

Activates B- CellActivates Cytotoxic

T- Cell

Memory B-CellMemory T-Cell

Kills Infected CellsAntibodies

Immune Response Explained

1. Antigen infects cells.2. Macrophage ingests antigen and displays portion on its surface.3. Helper T- Cell recognizes antigen on the surface of the

macrophage,binds to it, becomes sensitized and rapidly divides.4. Sensitized Helper T-Cell divide into Cytotoxic T-Cells, helper T-

cells, suppressor T-cells, or become memory T-cells.5. Active Cytotoxic T-Cells kill infected cells and memory T-cells

wait for a second infection of the same antigen.6. At the same time, B-Cells divide into Plasma Cells and Memory

B- Cells.7. Plasma cells produce antibodies that deactivate pathogen.8. Memory T and Memory B cells remain in the body to speed up

the response if the same antigen reappears.9. Supressor T-Cells stop the immune response when all antigens

have been destroyed.

Immune Response Summary

Antigen

Macrophage

Helper T - Cell

Active Cytotoxic T-Cell Active B - Cell

Kills Infected Cells Plasma Cell Memory B-Cell

Antibodies

Deactivates AntigensHarmless/agglutinate/destruction

Memory T-cell

Displays copy of antigen on surface of cell

Cellular Immunity Antibody Immunity

Cellular Immunity .vs. Antibody Immunity

• Carried out by T-Cells

• Infected cells are killed by Cytotoxic T –Cells.

• Carried out by B-cells

• Antibodies are produced and dumped into blood stream.

• Antibodies bind to antigens and deactivate them.

Cellular Immunity (cell-mediated) Antibody (Humoral) Immunity

Antibodies

• Y-shaped protein molecule.• Made up of variable and

constant regions.• Made up of Heavy and

Light chains.• Produced by B-

Lymphocytes• Function: Recognize

antigens, bind to and deactivate them.– Note: Variable region

recognizes the anitgens.

How an antibody operates/works

Deactivation of a bacterium by an antibody.

Primary .vs. Secondary Immune Response

• Primary Immune Response– This is a response to an invader the First time the invader

infects the body.• No measurable immune response for first few days.

• Next 10 – 15 days antibody production grows steadily

• Secondary Immune Response– A more rapid response to an invader the 2nd time it invades

the body.• Antibody production increases dramatically and in a much shorter

time period..

Primary .vs. Secondary Immune Response

Development of Immunity

• Inherited immunity– Genetic factors that affect baby before birth

• E.g. giving tetanus to mothers so babies can inherit this protection via placenta

• Acquired immunity: resistance after birth– Natural

– Artificial

Development of Immunity

1. Natural ImmunityThis is immunity that occurs whenever an animal is naturally exposed to a

pathogen. Natural immunity can be active or passive.active: when the animal’s own immune system encounters a pathogen and mounts an immune responsepassive: when antibodies are given to a person or animal from the blood or colostrum from another person or animal.*this type of immunity only lasts for a short period of time.* Colostrum is major source of antibodies in young puppies

2. Artificial ImmunityThis is immunity where a deliberate exposure to the pathogen is created (i.e. vaccinations). An injection of a weakened strain of an infectious microbe (pathogen) causes the body to undergo an immune response. This is also an example of active immunity.

Autoimmune Disease

• Autoimmune diseases are diseases where the immune system begins to attack itself.– Ex:

• Autoimmune Hemolytic Anemia• Autoimmune skin diseases• Systemic Lupus Erythematosus

• Cause(s): unknown• Cures/Treatments: No known cures. Usually treated with

drugs (steroids, other immunomodulating drugs,etc).

Allergies

Allergy- An exaggerated response by the immune system to an allergen.

Allergen: a normally harmless substance that causes an allergic reaction.ex: dust, pollen, mould, food, insect stings

Types of Allergic reactionsThere are two types of allergic reactions.

a. Immediate – occurs within seconds and normally lasts for about 30 mins.b. Delayed – takes longer-hours to days- to react and can last for a much longer time.

What happens during an allergic reaction?

• During an allergic reaction antibodies cause histamines to be released from certain cells.

Histamines cause:a. Swelling of tissuesb. Release of fluids (runny noses and eyes)c. muscle spasms (some cases)d. vasodilation (heat)

Anaphylaxis or anaphylactic shock:This is the sudden and severe allergic reaction to a substance that can cause death.

Treatments for Allergies1. Avoidance of allergen – especially food.2. Epinephrine – “epi-pen”3. Antihistamines -- benadryl