THE IMMUNE SYSTEM

Students should be able to:Describe the role of the blood in defending the bodyExplain how the principles of immunization are used to control communicable disease

T E R M IN O L O G Y• A N T IB IO T IC S : A drug used to treat infections

caused by bacteria and other microorganisms (inhibits growth or destroys).e.g. penicillin, streptomycin, tetracycline

• A N T IG E N : A toxin or other foreign substance that induces an immune response in the body, esp. the production of antibodies.

• A N T IB O D Y : A blood protein produced in response to and counteracting a specific antigen

• A N T I-TO X IN : An antibody that counteracts a toxin. (antidote)

• IM M U N ITY : The ability to resist a particular toxin by the action of specific antibodies.

• IM M U N IZ A T IO N : the act of making immune (especially by inoculation, i.e. taking a vaccine as a precaution against contracting a disease).

• V A C C IN E : A substance used to stimulate the production of antibodies and provide immunity against one or several diseases, prepared from the causative agent of a disease, its products, or a synthetic substitute, treated to act as an antigen without inducing the disease.

• V A C C IN A T IO N : taking a vaccine as a precaution against contracting a disease

FIRST LINE OF DEFENSE• Goal: to stop pathogens from entering the bodySkin – acts as a barrier to invasionSweat – has chemicals which can kill different

pathogens. Tears - have lysozyme which has powerful

digestive abilities that render antigens harmless. Saliva – also has lysozyme.Mucus - can trap pathogens, which are then

sneezed, coughed, washed away, or destroyed by chemicals.

Stomach Acid – destroys pathogens

SECOND LINE OF DEFENSE• If a pathogen is able to get past the body's first

line of defense, and an infection starts, the body can rely on it's second line of defense.

• First there is a non-specific response (phagocytosis) followed by an INFLAMMATORY RESPONSE.

• Phagocytosis = ingestion + digestion of pathogens.

• Phagocytic leucocytes (macrophages) engulf pathogens.

InflammationInflammation causes:

ii.Redness - due to capillary dilation resulting in increased blood flow

iii.Heat - due to capillary dilation resulting in increased blood flow

iv.Swelling – due to passage of plasma from the blood stream into the damaged tissue

v. Pain – due mainly to tissue destruction and, to a lesser extent, swelling.

THIRD LINE OF DEFENSE• Sometimes the second line of defense is still not enough

and the pathogen is then heading for the body's last line of defense, the immune system.

• The immune system recognizes, attacks, destroys, and remembers each pathogen that enters the body. It does this by making specialized cells and antibodies that render the pathogens harmless.

• Unlike the first line and second line defense the immune

system differentiates among pathogens.

• For each type of pathogen, the immune system produces cells that are specific for that particular pathogen.

• The Immune System includes all parts of the body that help in the recognition and destruction of foreign materials.

• Parts of the immune system: white blood cells(phagocytes

and lymphocytes) bone marrow lymph nodes tonsils thymus spleen

TYPES OF IMMUNITYP A S S IV E

• Source: It is developed when ready-made antibodies are inoculated from outside.

• Side effects: It may cause reaction.

• Period of relief: It provides immediate relief.

• Period of effectiveness: It is short lived

A C T IV E

• Source: It is developed by an individual’s own cells in response to an infection or a vaccine.

• Side effects: It has no side effects.

• Period of relief: It provides relief only after long period.

• Period of effectiveness: It is long lasting.

• The natural passive immunity occurs, when the maternal IgG type antibodies is passed to the foetus through the placenta. It is very much helpful in the initial 6 months of the infant’s life when the immune system is still developing.

• In the artificial passive immunity, we are introducing immunoglobulin or pre formed animal based antibodies (antiserum) to a non immune person. This can be used, following exposure, to a pathogen.

• It is named as naturally acquired active immunity because, the person develops the full fledged infection to the organism and later finds himself resistant to that organism.

• In the artificial acquired active immunity, the patient is introduced with an organism (usually attenuated) along with substances to activate the immune response.

DISEASES OF THE IMMUNE SYSTEM

• HAY FEVERHAY FEVER: is your immune system's response to foreign material in the air you breathe.

• Hay fever usually refers to allergies to outdoor, airborne materials such as pollens and molds.

• A particular kind of antibody, IgE is released causing very sensitive reaction to the allergens.

• Histamine is produced resulting sneezing, difficulty breathing, runny nose.

• Antihistamines and inhalers relieve symptoms.

• ASTHMAASTHMA: is a disorder that causes the airways of the lungs to swell and narrow, leading to wheezing, shortness of breath, chest tightness, and coughing.