Allergies are the result of your immune system's response to a substance. Immune responses can be mild, from coughing and a runny nose, to a life-threatening reaction know as anaphylaxis.  A person becomes allergic when their body develops antigens against a substance. The purpose of the immune system is to defend itself and keep microorganisms, such as certain bacteria, viruses, and fungi, out of the body, and to destroy any infectious microorganisms that do invade the body. The immune system is made up of a complex and vital network of cells and organs that protect the body from infection. The organs involved with the immune system are called the lymphoid organs. They affect growth, development, and the release of lymphocytes (a type of white blood cell). The blood vessels and lymphatic vessels are important parts of the lymphoid organs. They carry the lymphocytes to and from different areas in the body. Each lymphoid organ plays a role in the production and activation of lymphocytes. Lymphoid organs include: Adenoids (two glands located at the back of the nasal passages) Appendix (a small tube that is connected to the large intestine) Blood vessels (the arteries, veins, and capillaries through which blood flows) Bone marrow (the soft, fatty tissue found in bone cavities) Lymph nodes (small organs shaped like beans, which are located throughout the body and connect via the lymphatic vessels) Lymphatic vessels (a network of channels throughout the body that carries lymphocytes to the lymphoid organs and bloodstream) Peyer's patches (lymphoid tissue in the small intestine) Spleen (a fist-sized organ located in the abdominal cavity) Thymus (two lobes that join in front of the trachea behind the breast bone) Tonsils (two oval masses in the back of the throat) Lymphoid organs include: Adenoids (two glands located at the back of the nasal passages) Appendix (a small tube that is connected to the large intestine) Blood vessels (the arteries, veins, and capillaries through which blood flows) Bone marrow (the soft, fatty tissue found in bone cavities) Lymph nodes (small organs shaped like beans, which are located throughout the body and connect via the lymphatic vessels) Lymphatic vessels (a network of channels throughout the body that carries lymphocytes to the lymphoid organs and bloodstream) Peyer's patches (lymphoid tissue in the small intestine) Spleen (a fist-sized organ located in the abdominal cavity) Thymus (two lobes that join in front of the trachea behind the breast bone) Tonsils (two oval masses in the back of the throat) Anaphylactic shock, also called anaphylaxis, is a severe, life-threatening reaction to certain allergens. Body tissues may swell, including tissues in the throat. Anaphylactic shock is also characterized by a sudden drop in blood pressure. The following are the most common symptoms of anaphylactic shock. However, each person may experience symptoms differently.

2. • Allergies are the result of your
immune system's response to a
substance. Immune responses
can be mild, from coughing and a
runny nose, to a life-threatening
reaction know as anaphylaxis.
• A person becomes allergic
when their body develops
antigens against a substance.

3. • The purpose of the immune system is to defend itself and keep
microorganisms, such as certain bacteria, viruses, and fungi, out of the body,
and to destroy any infectious microorganisms that do invade the body.
• The immune system is made up of a complex and vital network of cells and
organs that protect the body from infection.
• The organs involved with the immune system are called the lymphoid
organs. They affect growth, development, and the release of lymphocytes (a
type of white blood cell).
• The blood vessels and lymphatic vessels are important parts of the lymphoid
organs.
• They carry the lymphocytes to and from different areas in the body.
• Each lymphoid organ plays a role in the production and activation of
lymphocytes.

4. Lymphoid organs include:
•Adenoids (two glands located at the back of the nasal passages)
•Appendix (a small tube that is connected to the large intestine)
•Blood vessels (the arteries, veins, and capillaries through which blood flows)
•Bone marrow (the soft, fatty tissue found in bone cavities)
•Lymph nodes (small organs shaped like beans, which are located throughout the
body and connect via the lymphatic vessels)
•Lymphatic vessels (a network of channels throughout the body that carries
lymphocytes to the lymphoid organs and bloodstream)
•Peyer's patches (lymphoid tissue in the small intestine)
•Spleen (a fist-sized organ located in the abdominal cavity)
•Thymus (two lobes that join in front of the trachea behind the breast bone)
•Tonsils (two oval masses in the back of the throat)

5. • Anaphylactic shock, also called anaphylaxis, is a severe, life-threatening
reaction to certain allergens.
• Body tissues may swell, including tissues in the throat.
• Anaphylactic shock is also characterized by a sudden drop in blood
pressure.
• The following are the most common symptoms of anaphylactic shock.
• However, each person may experience symptoms differently.

6. symptoms may include:
Itching and hives over most of the body
Feeling warm
Swelling of the throat and tongue or tightness in throat
Difficulty breathing or shortness of breath
Dizziness
Headache
Pain or cramps
Nausea, vomiting, or diarrhea
Shock
Loss of consciousness
Feeling light-headed
Anxiety
Abnormal heart rate (too fast or too slow)

7.  IgE causes immediate (type I) hypersensitivities
› Characterized by immediate reaction of the
sensitized individual
 Generally within minutes of exposure
 Tendency to have type I hypersensitivities is
inherited
› Reactions occur in at least 20% to 30% of population

8.  Sensitization occurs when antigen makes contact
with some part of body and induces response
 IgE antibodies bind to receptors on mast cells and
basophiles
› Antigen readily bonds to cells fixed with IgE antibodies
 Within seconds, mast cells degranulate releasing mediators that
initiate immune reaction including hives, hay fever and
anaphylaxis

9.  Localized anaphylaxis
› Most allergic reactions are local
anaphylaxis
 Hives
 Allergic skin condition characterized by
formation of wheal and flare rash
 Hay fever
 Allergic condition caused by inhaled antigen
 Condition marked by itching teary eyes,
sneezing and runny nose
 Asthma
 Respiratory allergy
 Allergic mediators attracted to inflamed
respiratory tract
 Results in increased mucous secretion
and bronchi spasm

10.  Generalized anaphylaxis
› Rare, but more serious
› Antigen enters bloodstream and becomes
widespread
 Reactions affect almost entire body
 Can induce shock
› Massive release of mediators causes extensive
blood vessel dilation and fluid loss
 Causes fall in pressure leading to blood flow
insufficiency

11.  Immunotherapy
› General term for techniques
used to modify immune
system for favorable effect
› Procedure is to inject
individual with extremely
dilute suspension of
allergen
 Called desensitization or
hyposensitization
› Concentration of allergen
gradually increased over
time
 Individual gradually becomes
less sensitive

12.  Immunotherapy
› Second therapeutic procedure is injection of
antibodies to bind IgE
 Essentially anti-IgE antibodies
› Most IgE are bound to mast cells and basophiles
 Engineered anti-IgE created
 rhuMab = recombinant human Monoclonal antibody

13.  Complement-fixing antibodies react with cell
surface antigens causing cell injury or death
 Cells can be destroyed in type II reactions
through complement fixation and antibody-
dependent cellular cytotoxicity (ADCC)
 Examples of type II hypersensitivities are
› Transfusion reactions
› Hemolytic disease of the newborn

14.  Transfusion reactions
› Normal red blood cells have different surface antigens
 Antigens differ from person to person
 People are designated type A, B, AB or O
› Transfused blood that is antigenically different can be
lysed by recipient immune cells
› Cross-matching blood is used to ensure compatibility
between donor and recipient
› Antibody-coated cells removed by phagocyte system
› Symptoms include low blood pressure, pain, nausea and
vomiting

15.  Hemolytic disease of the newborn
› Basis of disease is incompatibility of Rh
factor between mother and child
 Rh factor RBC cell surface antigen
 Rh positive = Rh antigen present
 Rh negative = Rh antigen missing
 Anti-Rh antibodies form in Rh negative
mother pregnant with Rh positive fetus
 First Rh positive fetus unharmed
 Second Rh positive fetus provokes
strong secondary immune response
 IgG antibodies of secondary response
cross placenta causing extensive
damage to fetal red blood cells

16.  Immune complexes consist of antigen and antibody
bound together
 Usually adhere to Fc receptors on cells
› Complexes are destroyed and removed
 Certain instances complexes persist in circulation or at
sites of formation
› Initiate blood clotting mechanism
› Activate complement contributing to inflammation
 Complexes commonly deposited in skin, joints and
kidney
 Complexes also cause disseminated intravascular
coagulation (DIC)
› Clots in small vessels
 Leads to system failure

17.  Delayed hypersensitivities caused by cell-
mediated immunity
› Slowly developing response to antigen
 Reactions peak in 2 to 3 days instead of minutes
 T cells are responsible for reactions
› Reactions can occur nearly anywhere in the body
 Delayed hypersensitivity reactions responsible
for contact dermatitis, tissue damage, rejection
of tissue grafts and some autoimmune diseases

18.  Tuberculin skin test
› Test involves introduction
of small quantities of
protein antigens from
tubercle bacillus into skin
› In positive skin test
injection site reddens and
gradually thickens
 Reaction reaches peak in 2
to 3 days
› Reactions result from
sensitized T cells, release
of cytokines and influx of
macrophages

19.  Contact hypersensitivities
› Mediated by the T cells
 T cells release cytokines
 Cytokines initiate inflammation that
attracts macrophages
 Macrophages release mediators
to add to inflammation
› Common examples of contact
allergies include
 Poison ivy and poison oak
 Nickel in metal jewelry
 Chromium salts in leather
 Latex products

20.  Major drawback to graft transplantation is possible
immunological rejection
› Differences between donor and recipient tissues basis for
rejection
› Rejection is predominantly type IV reaction
 Killing of graft cells occurs through complex combination
of mechanisms
› Contact with sensitized cytotoxic T cells and natural killer cells
 Combination of agents commonly used to prevent graft
rejection
› Cyclosporin A
› Steroids
› Basiliximab
 Monoclonal antibody preparation
 Blocks binding of immune mediators

21.  Body usually recognizes self antigens
› Destroys lymphocytes that would destroy self
› Malfunction in immune recognition basis for autoimmunity
 Autoimmune diseases may result from reactions to
antigens that are similar to self antigens
 Autoimmunity may occur after tissue injury
› Self antigens released from injured organ
 Autoantibodies form and interact with injured tissues and cause
further damage

22.  Spectrum of autoimmune diseases
› Reactions occur over spectrum
 Organ-specific to widespread responses
› Organ-specific
 Thyroid disease
 Only thyroid is affected
› Widespread response
 Lupus
 Autoantibodies made against nuclear constituents
of all body cells
 Rheumatoid arthritis
 Immune response made against collagen in
connective tissue
 Myasthenia gravis
 Autoantibody-mediated disease
 Antibody to acetylcholine receptor proteins

23.  Treatment of autoimmune diseases
› Treatment aimed at:
 Killing dividing cells
 Immunosuppressant
 Controlling T cell signaling
 Cyclosporin
 Anti-inflammatory medications
 Cortisone-like steroids
 Replacement therapy
 Insulin

24.  Immunodeficiency disorders are marked by
the body’s inability to make and sustain an
adequate immune response
 Two basic types of disorders
› Primary or congenital
 Inborn as a result of genetic defect or
developmental abnormality
› Secondary or acquired
 Can be acquired as result of infection or other
stressor

25.  Primary immunodeficiencies
› Generally rare
› Examples
 Agammaglobulinemia
 Few or no antibodies produced
 Occurs in 1 in 50,000 people
 Severe combined immunodeficiency disorder (SCID)
 Neither B nor T lymphocytes are functional
 Occurs in 1 in 500,000 live births
 Selective IgA deficiency
 Little or no IgA produced
 Most common disorder
 One in 333 to 700 people

26.  Secondary immunodeficiencies
› Result from environmental, rather than genetic factors
 Malignancies, advanced age certain infections,
immunosuppressive drugs and malnutrition are just a few
› Often results from depletion of certain cells of the immune
system
 Syphilis, leprosy and malaria affect T-cell population and
macrophage function
 Malignancies of lymphoid system decrease antibody-mediated
immunity
› Most serious widespread immunodeficiency is AIDS
 Destroys helper T cells
 Inhibits initiation of cellular and antibody-mediated immunity