The document discusses acquired (adaptive) immunity, highlighting two main mechanisms: humoral immunity and cell-mediated immunity. It outlines the characteristics of acquired immunity, including specificity, diversity, and the role of memory cells in enhancing immune responses upon re-exposure to antigens. Furthermore, it differentiates between naturally and artificially acquired immunity, as well as the mechanisms through which antibodies function in humoral immunity.

1. Acquired Immunity
Acquired Immunity

2. Acquired (Adaptive) Immunity
Acquired (Adaptive) Immunity
Defensive mechanisms include :
Defensive mechanisms include :
1) Innate immunity
1) Innate immunity (Natural or Non specific)
(Natural or Non specific)
2) Acquired immunity
2) Acquired immunity (Adaptive or Specific
(Adaptive or Specific)
)
Cell
Cell-
-mediated immunity Humoral immunity
mediated immunity Humoral immunity

3. Aquired (specific) immunity
Aquired (specific) immunity
* The
* The acquired
acquired immune response is
immune response is more
more specialized
specialized
than
than innate
innate immune response
immune response
* The acquired immune response involves a combination
* The acquired immune response involves a combination
of two mechanisms :
of two mechanisms :
1) Humoral immune response
1) Humoral immune response
2) cell mediated immune response
2) cell mediated immune response
* They interact with one another to destroy foreign body
* They interact with one another to destroy foreign body
(microorganisms, infected cells, tumor cells)
(microorganisms, infected cells, tumor cells)

4. Aquired (specific) immunity
Aquired (specific) immunity
Two mechanisms
Two mechanisms
1) Humoral immune response:
1) Humoral immune response:
-
- Antibodies
Antibodies are produced by
are produced by B
B-
-lymphocytes
lymphocytes
-
- These have the ability to recognize and bind
These have the ability to recognize and bind
specifically to antigen that induced their formation
specifically to antigen that induced their formation
2) The cell mediated immune response (CMI)
2) The cell mediated immune response (CMI)
-
- It is mediated by certain types of
It is mediated by certain types of T
T-
-lymphocytes
lymphocytes
-
- T
T-
-lymphocytes recognize foreign material by
lymphocytes recognize foreign material by
means of
means of surface receptors
surface receptors
-
- T
T-
-lymphocytes attack and destroy foreign material
lymphocytes attack and destroy foreign material
directly or through release of soluble mediators
directly or through release of soluble mediators
i.e.
i.e. cytokines
cytokines

5. Characters Of Acquired Immune Response
Characters Of Acquired Immune Response
1) Highly specific
1) Highly specific for the invading organism
for the invading organism
2) Discrimination between “self and “non self” molecules
2) Discrimination between “self and “non self” molecules
The response only occurs to “non self” molecules
The response only occurs to “non self” molecules
3) Diversity:
3) Diversity:
-
- It can respond to millions of different antigens
It can respond to millions of different antigens
-
- Lymphoctes population consists of many different
Lymphoctes population consists of many different
clones (one cell and its progny)
clones (one cell and its progny)
-
- Each clone express an antigen receptor and
Each clone express an antigen receptor and
responds only to one antigenic epitope
responds only to one antigenic epitope

6. Characters Of Acquired Immune Response
Characters Of Acquired Immune Response
4) Response amplified following repeated exposure to
4) Response amplified following repeated exposure to
the same pathogens
the same pathogens
5) Memory cells ( B and T cells) generated.
5) Memory cells ( B and T cells) generated.

7. Mechanism Of Acquired Immune Response
Mechanism Of Acquired Immune Response
Acquired immune response is initiated by:
Acquired immune response is initiated by:
* Recognition of the antigen by specific lymphocytes
* Recognition of the antigen by specific lymphocytes
* Activation of these specific lymphocytes
* Activation of these specific lymphocytes
* Proliferation and differentiation into effector cells;
* Proliferation and differentiation into effector cells;
-
-The effector cells eliminate the antigen
The effector cells eliminate the antigen
-
-Return of homeostasis and development of memory cells
Return of homeostasis and development of memory cells
* Memory cells evoke a more rapid and long response on
* Memory cells evoke a more rapid and long response on
re
re-
-exposure to same antigen
exposure to same antigen

8. Acquired Or Adaptive Immunity
Acquired Or Adaptive Immunity
I
I-
- Passive
Passive acquired
acquired immunity
immunity
a
a-
-Naturally
Naturally passive
passive acquired
acquired immunity
immunity
Antibodies
Antibodies are
are passed
passed through
through placenta
placenta
to
to the
the fetus
fetus
b
b-
- Artificially passive acquired immunity
Artificially passive acquired immunity
The injection of alredy prepared antibodies,
The injection of alredy prepared antibodies,
such as gamma globulin
such as gamma globulin
(short
(short-
-term immunization)
term immunization)

9. II
II-
- Active acquired immunity
Active acquired immunity
a
a-
-Natural
Natural active
active acquired
acquired immunity
immunity :
:
-
- Following
Following clinical
clinical or
or subclinical
subclinical infections
infections
-
- measles
measles or
or mumps,
mumps, in
in which
which immunity
immunity is
is
long
long lasting
lasting
b
b-
- Artificial
Artificial active
active acquired
acquired immunity
immunity :
:
-
- Following
Following vaccination
vaccination with
with live
live or
or killed
killed
infectious
infectious agents
agents or
or their
their products
products

10. Mechanism of Humoral immunity
Mechanism of Humoral immunity
* Antibodies induce resistance through:
* Antibodies induce resistance through:
1) Antitoxin neutralize bacterial toxins (diphtheria,tetanus)
1) Antitoxin neutralize bacterial toxins (diphtheria,tetanus)
Antitoxin are developed actively as a result of:
Antitoxin are developed actively as a result of:
a
a-
- Previous infection
Previous infection
b
b-
- Artificial immunization
Artificial immunization
c
c-
- Transferred passively as antiserum
Transferred passively as antiserum
* Neutralization of toxin with antitoxin prevents a
* Neutralization of toxin with antitoxin prevents a
combination with tissue cells
combination with tissue cells

11. Mechanism of Humoral immunity
Mechanism of Humoral immunity
2) Antibodies attach to the surface of bacteria and
2) Antibodies attach to the surface of bacteria and
a
a-
- act as opsonins and enhance phagocytosisd
act as opsonins and enhance phagocytosisd
b
b-
- prevent the adherence of microorganisms to
prevent the adherence of microorganisms to
their target cells, e.g. IgA in the gut
their target cells, e.g. IgA in the gut
c
c-
- Activate the complement and lead to bacterial lysis
Activate the complement and lead to bacterial lysis
d
d-
- Clump bacteria (agglutination) leading to
Clump bacteria (agglutination) leading to
phagocytosis
phagocytosis