all about immunity and host defense mechanisms

2. • The term immunity refers to the resistance exhibited by
the host towards infection caused by micro organisms
and their products(toxins).
• This is based on the property of self and non self
recognition.
• That means immunity is carried out by the process of
recognition and disposal of non self or materials that
enter the body.
• Immune response is the reaction of the body against any
foreign antigen.
• But protection against infection disease is only a part of
it. 2

4. (McGrawhill,2015)
4

6. • An antibody or immunoglobulin (Ig) is a glycoprotein
that is made by plasma cells in response to an antigen
and can recognize and bind to the antigen that caused
its production.
• There are five types of antibodies
 IgG
 IgE
 IgD
 IgM
 IgA

7. Functions:
Immunity to new born.
Potent activator of
complement system.
Neutralization of toxins.
IgG3 binds to Fc
receptors-
phagocytosis.
Functions:
Activation of classical
pathway.
Defense against
multivalent bacterial
antigens.
Acts as opsonin.
Present on B-cell surface,
acts as antigen receptor.

8. Functions:
 Secretary antibody.
 Effective against bacterial
like
 Salmonella,
 Vibrio cholerae,
 Niesseria gonorrhoea, etc.
 Effective against viruses like
those causing Poliomyelitis &
Influenza.
 Protection to infant gut.
Functions:
 B cell activation .
 Acts as receptor for Ag binding.
Functions:
 Responsible for immediate
hypersensitivity or allergic reactions.
 Binds to Fc receptors on basophils and
mast cells.
 Release of substances like histamine ,
bradykinin and other vasoactive
mediators’.

9. • A vaccine is a biological preparation that improves immunity to a
particular disease. It contains certain agents that not only resembles a
disease-causing microorganism but it also stimulates body’s immune
system recognize the foreign agents.
• Vaccines are dead or inactivated organisms or purified products derived from
them. There are several types of vaccines in use. They are:
Whole-Organism Vaccines
 Killed
 Attenuated
 Purified Macromolecules as Vaccines
 Toxoids
 Capsular polysaccharides
 Recombinant microbial antigens/Surface antigens
 Recombinant vaccine
 DNA vaccine
 Multivalent Subunit Vaccines

10. • Allergy refers to certain diseases in which immune responses
to environmental antigens cause tissue inflammation and
organ dysfunction. Hypersensitivity and sensitivity are
synonyms for allergy.
• Allergen is any antigen that causes allergy. The allergen is
either inhaled or ingested and is then processed by the
dendritic cell, an antigen-presenting cell.
• It can be complete protein antigens or low molecular weight
proteins capable of eliciting an IgE response. Pollen and
animal dander represent complete protein antigens.
• Atopy is the inherited propensity to respond
immunologically to such common naturally occurring
allergens with continuous production of IgE antibodies.

11. Allergic Reaction Its overreaction to a harmless substance (an allergen)
This harmless substance that is contacted through the skin,
inhaled into the lungs, swallowed, or injected.

12. •Allergy skin testing may be used to identify the allergens that
are causing your allergy symptoms.
• The test is performed by pricking your skin with an extract of
an allergen, and then checking the skin's reaction.
•If a skin test cannot be performed, a radioallergosorbent blood
test (RAST) may be taken.
• This test is not as sensitive as a skin test. The RAST evaluates
the number of antibodies produced by the immune system.
•Higher levels of certain antibodies can identify particular
allergies
Hypersensitivity reactions require a pre-sensitized (immune)
state of the host. Hypersensitivity reactions can be divided into
four types: type I, type II, type III and type IV, based on the
mechanisms involved and time taken for the reaction.
Frequently, a particular clinical condition (disease) may involve
more than one type of reaction.

13. •Type I hypersensitivity is also
known as immediate or anaphylactic
hypersensitivity. The reaction may involve
skin (urticaria and eczema), eyes
(conjunctivitis), nasopharynx (rhinorrhea,
rhinitis), bronchopulmonary tissues
(asthma) and gastrointestinal tract
(gastroenteritis).
•The reaction may cause a range of
symptoms from minor to death.
• The reaction usually takes 15 - 30
minutes from the time of exposure to the
antigen, although sometimes it may have
a delayed onset (10 - 12 hours).
•Immediate hypersensitivity is mediated
by IgE .

14. •Type II hypersensitivity is also
known as cytotoxic hypersensitivity and
may affect a variety of organs and
tissues.
• The antigens are normally endogenous,
although exogenous chemicals
(haptens) which can attach to cell
membranes can also lead to type II
hypersensitivity.
•e.g. Drug-induced hemolytic anemia ,
granulocytopenia and
thrombocytopenia .
•The reaction time is minutes to hours.
Type II hypersensitivity is primarily
mediated by antibodies of the IgM or IgG
classes and complement. Phagocytes and
K cells may also play a role (ADCC). The
lesion contains antibody, complement
and neutrophils.

15. Type III Hypersensitivity
•The reaction may be general e.g., serum
sickness or may involve individual organs
including: e.g. kidney (lupus nephritis)
•The reaction may take 3 - 10 hours after
exposure to the antigen .It is mediated by
soluble immune complexes. They are mostly
of the IgG class, although IgM may also be
involved.
•The antigen may be exogenous or
endogenous
•The antigen is soluble and not attached to
the organ involved.
•The damage is caused by platelets and
neutrophils.
•The lesion contains primarily neutrophils
and deposits of immune complexes and
complement.
•Macrophages infiltrating in later stages may
be involved in the healing process.

16. •Type IV hypersensitivity is also known as cell mediated or delayed type hypersensitivity .
•e.g. Tuberculin reaction which peaks 48 hours after the injection of antigen (PPD) or (old
tuberculin). The lesion is characterized by induration and erythema.
•Type IV hypersensitivity is involved in the pathogenesis of many autoimmune and infectious
diseases (tuberculosis, leprosy, blastomycosis, histoplasmosis, toxoplasmosis, leishmaniasis) and
granulomas due to infections and foreign antigens. Another form of delayed hypersensitivity is
contact dermatitis (poison ivy , chemicals, heavy metals, etc.) in which the lesions are more
papular.

17. Antihistamines
• When medicine is needed to stem allergy symptoms, antihistamines are often first in line.
(Allegra,Zyrtec)
Decongestants (SUDAFED)
Anticholinergic Nasal Allergy Sprays
• Atrovent nasal spray can help with certain allergy symptoms.
Steroid Nasal Sprays
• Steroid nasal sprays are one of the strongest allergy medications. (Flonase,Nasonex)
Allergy Eye Drops
Mast Cell Inhibitors
• This type of medication can help but it’s all in the timing.
Allergy Shots
• For some people, allergy shots can mean the end to allergy medication.
Skin Allergies
• Advanced Reading: This article, written for doctors, provides in-depth information on skin
allergy treatments.
Dehumidifiers for Allergies
• For mold, mildew, or dust mite allergies.

18. •Rakel RE. Textbook of Family Medicine. 7th ed. Philadelphia, Pa: WB Saunders;
2007. [Accessed september 28, 2016].
•American Gastroenterological Association medical position statement: guidelines
for the evaluation of food allergies .Gastroenterology .2001 Mar;120(4):1023-5.
[Accessed september 28, 2016].
•Adkinson NF Jr .Middleton’s Allergy: Principles and Practice .6 th ed. Philadelphia,
Pa: Mosby; 2003 [Accessed september 28, 2016].
•Cooper, G.M. & Hausman, R.E., 2009. The Cell: A Molecular Approach, ASM Press.
Available at: https://books.google.com/books?id=YShGPgAACAAJ&pgis=1 [Accessed
September 28, 2016].
•Silverstein, A., Silverstein, V.B. & Nunn, L.S., 2009. Cells, Twenty-First Century
Books. Available at: https://books.google.com/books?id=Ro0ijFCmIq0C&pgis=1
[Accessed september 28, 2016].
•Strelkauskas, A. et al., 2015. Microbiology: A Clinical Approach, Second Edition,
Garland Science. Available at:
https://books.google.com/books?id=Rv0pCgAAQBAJ&pgis=1 [Accessed september
29, 2016].
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