THE IMMUNE SYSTEM

UNIT 7 IMMUNITY AND VACCINES VETERINARY ASSISTING PROGRAM

RESPONSIBILITIES • The immune system is responsible for protecting the

animal from potentially harmful organisms attempting to invade.

• It is a VERY complicated system• It must be able to recognize substances that are foreign to

the body by recognizing what is naturally occuring

ANTIGENS• Antigens are large, complex molecules that are foreign to

the body. • Once they enter the body, the stimulate an immune

response for which antibodies are made.• Antibodies: specific protein produced to protect against a

disease. Attacks the pathogen.• Pathogen: microorganism that causes disease

LYMPHATIC TISSUE• The body has lymphatic

tissue distributed throughout to detect antigens quickly.

• Within the lymphatic system are lymph nodes, which is lymph tissue encased in connective tissue.

• These lymph nodes can be palpated on almost any dog.

• Location of Lymph Nodes in the Dog. Digital image. Immune System Tumors in Dogs. Merck Manuals, July 2011. Web. 22 Aug. 2014.

• Large reddish-brown organ within the abdomen that is involved in the immune system and filtering blood.

• Contains areas where immune cells scan incoming blood for antigens.

• Houses the cells responsible for producing antibodies.

• Important but not necessary• Lymph nodes also house the cells

responsible for antibodies and other organs also help filter the blood

• If damaged, extensive bleeding can occur• Common site for tumors

Digital image. Lymphatic System Anatomy and Function. PetEducation, n.d. Web. 22 Aug. 2014.

SPLEEN

BONE MARROW• Essential for the immune system• Produces WBC’s • Complicated process

• When the body recognizes an antigen, neutrophils and macrophages phagocytize the antigen

• It is then broken down within the cell• A substance is release to begin immune response.• This release kills the virus or slows replication, attracts

other immune cells to the area, and kills the already damaged cells.

• This substance also affects the hypothalamus

LYMPHOCYTES AND ANTIBODIES

Specific lymphocytes come in contact with specific antigens• Stimulates repeated mitosis

• Results in a large number of lymphocytes • Designed to react to this particular antigen, this is called clonal expansion.

B lymphocyte or B cellB cells plasma cells secrete antibodies=humoral immunity• Antibody is Y shaped, arms of the Y detect the antigen• Pathogens have many antigenic determinate sites on its surface to which

antibodies bind• Antigen-antibody complex stimulates phagoctyic cells so pathogens are

phagocytized (destroyed)• T-Cells- type of lymphocyte associate with cell-mediated immunity

Antibodies are produced primarily in the lymph nodes but also in the spleen and bone marrow.

HYPOTHALAMUS• Any time the hypothalamus if affected, it elevates the

body temperature. FEVER!• Fever is designed to aid in the fighting of the pathogen• A high body temperature hinders the replication of an

infectious organism or can even kill it.• It also stimulates the activity of lymphocytes, phagocytes,

and antibodies.

INFLAMMATION• Can be a result of physical injuries or reaction to invasion

of a pathogen• This response delivers more WBC’s and antibodies to the

infected area• 4 signs of inflammation

• Pain• Heat• Redness • Swelling

• The swelling is referred to as edema. This is a build up of fluid under the skin due to increased capillary permeability.

INFECTION• Not antibody related, cell

mediated response only• This is when a large

number of cells invade a specific site

• A combination of WBC’s, invading pathogens, dying and destroyed tissue creates pus • When describing pus, the

term is purulent!!• Pus trapped in a pocket

is referred to as an abscess Digital image. Abscess on Dog's Shoulder.

BerryHaven Veterinary Group, n.d. Web. 22 Aug. 2014.

VACCINESIMMUNITY CONTINUED…

CREATING IMMUNITY• Immunity can occur one of two ways:

• Active immunity• Passive immunity

ACTIVE IMMUNITY• Active immunity results from exposure to a pathogen,

either through a vaccine or natural infection• Any exposure thereafter will trigger the immune system’s

memory and quickly destroy the pathogen• This can last for different periods of time, ranging from 6

months to years

Dog Receiving Vaccine. Digital image. Bordetella and Pets. VPI Veterinary Pet Insurance, n.d. Web. 22 Aug. 2014.

PASSIVE IMMUNITY• Immunity resulting from the transfer of antibodies from

one animal to another• Mother to offspring through colostrum• Commercial diets (Esbilac)• Plasma donation

• This immunity is temporary and usually only lasts several weeks to months

TYPES OF VACCINES1. Modified live vaccines

• Uses altered antigens created from a pathogen and places a small amount of the disease into the animal’s body

• Pathogen is weakened, so it can divide but not cause clinical disease

• Boosters can be given but not always needed2. Killed vaccines

• Uses killed pathogens• Can no longer divide but still has antigens to trigger an

immune response • Must get a booster• Slower

MLV

Vaccine box. Digital image. Nobivac Canine 1-DAPPv (Galaxy DA2PPv). Valley Vet Supplies, n.d. Web. 22 Aug. 2014.

KILLED

Rabies Vaccine Vial. Digital image. Nobivac 3 Rabies - 10 Dose Vial. KV Supply, n.d. Web. 22 Aug. 2014.

VACCINE ROUTES• Most vaccines come in an injectable form

• Subcutaneous • Intramuscular

• Others are intranasal (Bordetella)

Intranasal Vaccine. Digital image. Kennel Cough. MarvistaVet, 11 Dec. 2012. Web. 22 Aug. 2014.

ALLERGIC REACTIONS• Not all immune responses are to prevent disease. Some

occur against antigens that are not harmful• Allergens are substances that create an allergic response,

such as pollens, dust mites, and flea saliva• An animal’s sensitivity to this causes a release of

histamine. This release causes itchiness, eye and nasal discharge, sneezing, rubbing at eyes, and redness of the skin.

• Drugs given to help treat this are antihistamines • Atopy is an allergic condition of the skin involving

pruritus and alopecia

SEVERE ALLERGIC REACTIONS• An allergic reactions that is generalized and life

threatening is called anaphylaxis. • Causes bronchoconstriction and leaky vessels which lead

to respiratory distress and shock• Epinephrine counteracts physiologic effects of histamine.• Must be given quickly!

TITER• These tests measure the level of antibodies in the

bloodstream against a specific disease• Results are reported as a ratio

• A titer of 1:256 has more antibodies than 1:64• A high titer proves that an animal has been exposed to a

pathogen• Not when the exposure occurred, could be from a vaccine

REVIEW• Lymphatic is a highly complex system with lymph nodes

throughout the entire body• Many organs are involved with the immune system• Infection is not antibody related• Vaccines can be killed or modified live• The types of immunity are passive and active• Allergens can cause a life threatening event known as

anaphylaxis