IMMUNITY
DEFINITION OF IMMUNITY
It is the protective response provided by the body’s immune system
against an infection, injury, or trauma. It is the defence mechanism of
an organism.
TYPES OF THE IMMUNE SYSTEM
There are two main types of immune system:
a) External immune system
b) Internal immune system
a) External Defence System: It is of three types:
• i) Physical (Example: Epithelia of skin that cover the airways are
an effective barrier to pathogen).
• ii) Chemical (Example: Hydrochloric acid in the stomach kills
bacteria that gets ingested while we eat and drink).
• iii) Cellular (Example: Blood clotting factors (proteins) that are
produced by liver cells prevent the loss of blood and the entry of
pathogens through wounds).
b) Internal Defence System: It is of two types:
• i) Cellular (Example: Leucocytes and lymphocytes recognizes
pathogens and kill them).
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, • ii) Antibodies (Example: Antibodies are proteins that specifically
binds to target antigens and neutralizes their pathogenic effect).
Definition of Antigen: Any molecule that the body recognizes as
foreign.
Definition of Antibody: A glycoprotein made by plasma cells
derived from B-lymphocytes, secreted in response to an antigen.
Immune Response: It is the response of lymphocytes to the
presence of a foreign antigen.
TYPES OF WHITE BLOOD CELLS: There are two types of
white blood cells (Figure 1).
1) Phagocytes (neutrophils and macrophages) Produced in
2) Lymphocytes bone marrow
Figure 1: Structure of phagocyte and lymphocyte
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DEFINITION OF IMMUNITY
It is the protective response provided by the body’s immune system
against an infection, injury, or trauma. It is the defence mechanism of
an organism.
TYPES OF THE IMMUNE SYSTEM
There are two main types of immune system:
a) External immune system
b) Internal immune system
a) External Defence System: It is of three types:
• i) Physical (Example: Epithelia of skin that cover the airways are
an effective barrier to pathogen).
• ii) Chemical (Example: Hydrochloric acid in the stomach kills
bacteria that gets ingested while we eat and drink).
• iii) Cellular (Example: Blood clotting factors (proteins) that are
produced by liver cells prevent the loss of blood and the entry of
pathogens through wounds).
b) Internal Defence System: It is of two types:
• i) Cellular (Example: Leucocytes and lymphocytes recognizes
pathogens and kill them).
Page 1 of 12
, • ii) Antibodies (Example: Antibodies are proteins that specifically
binds to target antigens and neutralizes their pathogenic effect).
Definition of Antigen: Any molecule that the body recognizes as
foreign.
Definition of Antibody: A glycoprotein made by plasma cells
derived from B-lymphocytes, secreted in response to an antigen.
Immune Response: It is the response of lymphocytes to the
presence of a foreign antigen.
TYPES OF WHITE BLOOD CELLS: There are two types of
white blood cells (Figure 1).
1) Phagocytes (neutrophils and macrophages) Produced in
2) Lymphocytes bone marrow
Figure 1: Structure of phagocyte and lymphocyte
Page 2 of 12
