“ 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, 14 TH DALAI LAMA CHOOSE HAPPINESS!

PLEASE REFER TO PAGES 1-5 OF YOUR COMMON DISEASES OF COMPANION ANIMALS BOOK AND CHAPTER 9 IN YOUR CLINICAL ANATOMY AND PHYSIOLOGY BOOK THE IMMUNE SYSTEM System of defense against pathogens

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

Foreign Invaders Pathogens – Viruses, bacteria or other living thing that causes disease/immune response. Antigens – Soluble substances: Toxins & foreign proteins – Particulate: Bacteria/ tissue cells

Parts of the Immune System 1. Blood - particularly White Blood Cells 2. Bone Marrow – Produces B Lymphocytes and T lymphocytes 3. Thymus Gland – consist of T Lymphocytes (originally produced in the bone marrow) – T lymphocytes learn to recognize self from non-self – Mature and then move to spleen, lymph nodes looking for invaders 4. Other factors: nutrition, stress, sanitation, and age

Nonspecific Immunity vs. Specific Immunity Immunity Nonspecific: responds to all Pathogens in the same manner Species resistance Mechanical & Chemical Barriers Inflammatory response Interferon & Complement Specific: Response to pathogens is specific for that pathogen Humoral: B lymphoctyes & antibody production Cell-mediated: T-lymphocytes

NON-SPECIFIC IMMUNITY NONSPECIFIC IMMUNITY includes species resistance, mechanical/chemical barriers, inflammation, & interferon/complement 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 –Inflammation  When invaders gain access to the body there is an inflammatory response SIGNS OF INFLAMMATION: REDNESS HEAT PAIN SWELLING *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). NON-SPECIFIC IMMUNITY

NONSPECIFIC IMMUNITY Inteferon – Substance that prevents replication of virus in the host cell Complement – Group of enzymes activated during infections – Act on cell wall > pores in membranes > rupture/lysis of the cell

NONSPECIFIC IMMUNITY

SPECIFIC IMMUNE RESPONSE 3 RD Line of Defense: Specific Immune Response  Conducted by cells known as lymphocytes  T lymphocytes and B lymphocytes

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.  Upon contact with a specific antigen, cloning of B-cells creates some plasma cells which make ntibodies, while others become memory cells  Response time is slower on the first exposure to the antigen (7-10 days)  Subsequent exposure to the antigen initiates a quicker response due to the presence of memory cells

SPECIFIC IMMUNE RESPONSE 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  T-cells learn “self” from “non-self” in the thymus  Macrophages will present foreign antigen to the T-cell  T-cells will repeatedly divide and begin to destroy the invading organisms.  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- Cell Activates Cytotoxic T- Cell Memory B-Cell Memory T-Cell Kills Infected Cells Antibodies 

Immune Response Summary Antigen Macrophage Helper T - Cell Active Cytotoxic T-CellActive B - Cell Kills Infected CellsPlasma CellMemory B-Cell Antibodies Deactivates Antigens Harmless/agglutinate/destruction Memory T-cell Displays copy of antigen on surface of cell Cellular Immunity Antibody Immunity

Cellular Immunity vs. Humoral 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 antigens.

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 2 nd 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 Acquired  Natural – occurs every time the animal is exposed to a pathogen.  Artificial – the result of deliberate exposure to a pathogen such as with vaccinations. Passive  Antibodies formed in one infected animals are transferred to another animals that is not infected. Active  Occurs when the animal’s own immune system encounters a pathogen and produces an immune response