Immune system {immunology)
Immunity: is the ability of the body that defend against disease causing agents from the
body such as bacteria, fungi, virus and e.t.c
Immunology: is the study of the physiological defenses in which the body destroys or
neutralizes foreign matter (both living and nonliving things).
Immune defense system perform the following functions in below
I. It protects against foreign microbes from the body.
II. It Isolates or removes from the body non microbial foreign substances.
III. It destroys cancer body cells by functional process called immune survaleince.
Immunity can be divided into two types of defenses as fallowing in below.
1. Nonspecific defense (innate immunity or genetic defense).
Nonspecific defense: it is the immunity or body’s defense mechanism that protects against any
foreign or cancer cells without need recognizing their specific characteristics.
Its mechanisms of protection are not unique for specific pathogens, so that it is called nonspecific
defense.
2. Specific defense (acquired immunity).
Specific immunity: it is the immunity that has specific recognition for unique or particular
micro-organisms that is done by lymphocytes. For example Immunity created by
vaccination
Nonspecific of defense
Nonspecific of defense consists of two of defenses of lines as fallowing in below
First line of defense: it is the first barrier against entry of foreign microorganisms to the
human body. It include the following parts in below
Walls and moats (surface defense); these are the first line of defense that consists of walls such as
skin, interferon, nkc,, phagocytes, and moats such as mucus in tracts of the body.
i. Walls (skin):- it is the outer most layer of the body and it is the first barrier
against penetration of microbes, for example skin.
The skin it has oil and sweat glands that give skin surface a PH of the 3 to 5 (acidic),
Skin prevents excessive loss of water from the body by evaporation.
ii. The Moats: - these are the mucous membranes in respiratory and digestive tracts
Moats consist of digestive tract, respiratory tract and blood clotting.
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Digestive tract it has saliva which contain lysozyme (acidic) and other intestinal enzyme which kill
microbes in the food.
a. Respiratory tract
The cells in the trachea secrete thick sticky mucus that traps microbes and dust in inhaled air.
Also the cilia lining in this passage sweep the mucus containing germs towards glottis with help
coughing, sneezing to expel germs out of the body
b. Blood clotting: clotting prevents entry of microorganisms and seals the wounds
c. Tear: tear secreted by lacrimal glands contain lysozyme enzyme that dilutes and digest microbes
d. Saliva: saliva washes microbes from surface of the mouth and it contains amylase enzyme
e. Urine: urine cleans the pathway of urethra in both males and females and it contains uric acid
f. Sebum: oily substance secreted by sebaceous glands make clean on the surface of skin
g. Hydrochloric acid:
Roaming and patrolling (second line of defense): it is second phase of the
nonspecific immunity that is also called cellular counter attack defense
It is the defense that consists of some white blood cells and chemical substances It responds to any
microbial infection of invaders.
ACTORS OF SECOND LINE DEFENSE
Interferons, Phagocytes, natural killers, complement proteins, inflammations and fever are the
common actors of second line defense.
These cells are distributed through all the body to fight infections and they are also stored in lymphatic
system. This defense works when the microorganisms breached through first line of defense.
The cells that destroy antigens
All the cells are originated from the bone marrow and there are two types of WBC defense.
Granulocytes (phagocytes) A Granulocyte (lymphocytes)
Neutrophils basophils eosinophils B cells T cells Nkc
Origin and mode of action of phagocytes
Phagocytes are nuetrophiphils they are produced and matured in bone marrow.
Neutrophils are the most numerous of leukocytes, they form 60% of wbc.
They are stored in bone marrow before maturation
Neutrophils increase in a number during infection times
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They travel through the body by squeezing the walls of capillaries towards the
site of infection.
They ingest and kill bacteria by phagocytosis by releasing H2O2 and lysozyme
enzymes.
They kill bacteria they form bus, so they are short lived cells.
Monocytes
Monocytes are immature macrophages in bone marrow
Monocytes leave the bone marrow and get into blood stream where they grow in size
and become mature now they are macrophages.
When they mature and settle in organs such as lungs, liver and lymph nodes they are
called macrophages
They initiate immune response
They are long lived cells
Macrophage means big eaters.
Phagocytosis: is the process in which neutrophils or macrophages engulf bacteria and
destroy it
STEPS OF Phagocytosis
1. Chemotaxis: is the process in which phagocytes attract and detect bacteria with helping
of activating factor such as histamine.
2. Attachment: the phagocytes and becteria attach together,
3. Vacuole of neutrophils is formed
4. Endocytosis occurs endocytosis: is the process in which neutrophils or macrophages
engulf bacterial cell, at lastly dead body cell, bacteria and dead neutrophils become bu
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