Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
L13: 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
Also known as acquired immunity, resist a particular foreign agents, moreover, specific
immune response improve on repeated exposure to the same agents, many characteristic
distinguish specific immunity from non- specific immunity:
1. Specificity: specific activity for each type of pathogens. Immunity is directed against
a particular pathogen or foreign substance.
2. Memory: when exposed to the same pathogen or substance the body reacts so
quickly that there is no notice able pathogenesis, 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.
Response results in immunologic memory very important characteristic feature that
the concept of vaccination depends on
3. Diversity: the system is able to generate an enormous diversity of molecules such as
antibodies that recognize billions of different antigens.
4. Discrimination between self and non self. The specific immune system always
responds only to non self antigens thus, does not attack human itself.
5. Response is antigen dependent.
6. 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).
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Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
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).
1-Humoral (antibody – mediated) immunity
It is antibody (Abs.) dependent and relies upon body fluids especially the lymph and
blood plasma to spread Abs. around the body. The Abs. is produced by B- lymphocyte and
it is thought that processing of B-cell occurs in bone marrow and fetal liver. There are five
classes of Abs. each are called immunoglobulin as fallow:
1-IgA (15% of total Abs. count) found in mucous secretion of respiratory and digestive
tract, vagina and in colostrums the substance is produced before the milk after delivery will
protect the baby for about six months.
2-IgD (less than 1%) appears to have a role in activating and suppressing lymphocyte
activity.
3-IgE
(less than 1%) it is mediator in allergic response, activate histamine secreting cells
and play role in parasitic infection.
4-IgG (75% of total count) stimulate phagocyte cells, activate the complement system and
neutralized toxins. It is the only Abs. that can cross the placenta and confer immunity on
the fetus.
5-IgM
(10% of total Abs.) this is the predominant early Abs. that activate in an initial
attack of Ag. Because of it is high number of antigen binding sites have 5 sites (Fig.) ,this is
important in an initial activation of B –cells macrophage and complement system .
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Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
Fig. sites of binding antibodies with antigens
2-Cell – mediated immunity
It is involved T- lymphocyte cell, that is originally derive from stem cells of the bone
marrow and then passes to the thymus gland in the chest, where they multiply. Cell –
mediated is based on the action of specific kinds of cell T- lymphocyte that directly attack
cells infected with viruses or parasites , transplanted cells or organs and cancer cells .Tlymphocyte can lyses these cells or release chemicals like cytokines that enhance specific
immunity and non- specific defenses such as phagocytes and inflammation.
The cells responsible for specific and non- specific immunity are leukocytes (meaning
white cell) from the stem cells which migrate to the other body sites undergo further
development, some become residents within tissues while others circulate in body fluids. In
figure below there are different types of leukocyte:
1-Lymphoid cells
Lymphocyte are major cells of specific immune system, lymphocyte can be divided into
three populations T, B and natural killer (NK) cells.
2- Mononuclear cells
There are two types of mononuclear: monocyte & macrophages are highly phagocytic
were engulfed & destroyed pathogenic M.O.
3- Granulocytes
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Nursing college, Second stage
Microbiology
Dr.Nada Khazal K. Hendi
Have irregular- shaped nuclei with 2-5 lobes and the cytoplasm matrix has granules
contain reactive substances which kill M.O. There are three types of granules: neutrophil,
acidophile, basophile.
LEUKOCYTES: White Blood Cells
Granular leukocytes (granules in
cytoplasm)
Nongranular leukocytes (do not have
granules in their cytoplasm)


non
Fig. Leukocytes types divisions
Lymphoid cells
mononuclear cells
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Nursing college, Second stage
Neutrophile
Microbiology
Dr.Nada Khazal K. Hendi
Acidophile
Basophile
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