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Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
L10: Immunology
Immunology: is the study of host's defense mechanisms against disease, also study the
interaction between human and disease agents (pathogenic microbes).
Antibody (Ab): a protein produce as a result of interaction with an Ag. It has the ability to
combine with Ag that stimulated its production.
Antigen (Ag) or immunogen is substance (pathogen) that react with Ab. Not all Ag induce
Ab production.
General functions of immune system
1. Defense against foreign invaders.
2. Autotolerance (unresponsiveness to the self tissues).
3. Surveillance: recognition and clearance of internal antigens (old damaged, or
mutagenic cells).
Types of Immunity
Immunity can be classified according to their specificity into:
1. Innate ( non specific) immunity
2. acquired or adaptive (specific) immunity
1. Innate ( non specific) immunity
The elements of the non specific immunity include:
1. Anatomical barriers (skin, intestinal movement and oscillation of respiratory tract).
2. Chemical factors, include fatty acids in sweat, lysozyme, phospholipids, pH, defensins
which are antimicrobial polypeptides secreted by wide variety of host cells.
3. Physiologic barriers: fever response to infection inhibits growth of many microbes.
4. Biological factors: include the normal flora of the (skin, genitourinary tract, GIT) can
prevent the colonization of pathogenic microbes by secreting toxin substances or by
competing with pathogens for nutrient or attachment to host cells.
Properties of Innate ( non specific) immunity
1.Present at birth & does not improve on repeated contact with the same infectious agent.
2.Non specifically protects against foreign substances.
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Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
3. response results in no immunologic memory.
4. Response is antigen- independent.
5. inborn resistance.
6. response is characterized by immediate maximal course and occurs at rapid rate.
7. not needs for time of recognition or helping from other components of immune system.
Example of Innate ( non specific) immunity
System/organ
Immune effectors mechanisms
Skin
Mechanically prevents entry of microbes. Sweat contain fatty acids
which denatures microbial cellular proteins
Saliva
Hydrolytic enzymes
Tears
Lysozymes
Lung
Cilia, lysozymes, surfactant (antimicrobial lipoproteins)
GIT
Gastric pH, bile acid, lysozymes, flusing normal flora
Genitourinary tract Low pH, normal bacterial flora
Blood
Phagocytosis, complement, acute phase proteins
Mucous
Mechanically prevent entry of microbes, normal bacterial flora
membranes
interfere with the attachment of pathogenic microbes to the mucous
memberans and consequently entry of pathogenic microbes into
body is prevented.
Acquired or adaptive (specific) immunity
the resistance, which absent at the time of first exposure to a pathogen, but develops after
being exposed to the pathogen is called acquired immunity. It includes specific cells of
the immune system that ate able recognize and response to the foreign materials. The
cells involved in this type of immunity are lymphocytes both T and B cells.
Properties of acquired or adaptive (specific) immunity
1. specific activity for each type of pathogens.
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Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
2. recognition to the specific sites on the foreign substances (Ag) needs at first a certain
time so innate immunity is faster than specific immunity but the later is more effective
and the program of the solid immunity against infectious disease depend on the activation
of specific immunity.
3. response results in immunologic memory very important characteristic feature that the
concept of vaccination depends on.
4. Response is antigen dependent.
5. the effectiveness toward antigens increases following subsequent exposure to the same
antigens. Thus second contact with the same antigens increases the immune response
through antibodies or sensitized memory cells.
Classification of acquired or adaptive (specific) immunity
According to the nature of components of immune mediated reactions:
A:Humoral immunity(HI): mediated by specific glycoproteins (immunoglobulins or Ab).
B: Cell mediated immunity (CMI): mediated by specific cells which are T lymphocytes.
Also, specific immunity can be classified according to the rout of acquirement into:
1. Natural immunity
A: passive (placental transfer of Ab).
B: Active (as response to the infection).
2.Artificial immunity
A: passive (administration of Ab e.g. antitoxin antibodies).
B: Active (vaccination: administration of attenuated live or killed foreign invaders to
stimulate the immune system).
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