The document summarizes the immune system and its components. It discusses the two types of immunity - innate and acquired. Innate immunity is inborn and provides broad protection but no memory. Acquired immunity develops over time, has memory, and involves antibodies from B cells and cytotoxic T cells. It also discusses hypersensitivity or allergies, which occur when the immune system inappropriately responds to antigens. Allergies can be immediate from antibodies or delayed from T cells and cause inflammation and tissue damage.

1. Blood Physiology
Immune system
Dr. Fawaz A. Mustafa
PhD in Medical Physiology and Pharmacology
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2. Immune system
• Immunity: is defined as the ability of human body to
resist against harmful chemicals such as toxins that
released by microorganism which tend to damage the
tissues & organs. Lymphocytes are key constituents of
the immune system. The lymphatic system includes
lymphocytes, lymph nodes, tonsils, spleen, thymus
gland, lymph and lymphatic vessels.
• There are two types of immune defense systems:

3. Immune system
1. Innate immunity.
2. Acquired (adaptive) immunity.
A-Innate immunity: in this type of immunity the body is
born with the ability to recognize and destroy certain
substances but cannot distinguish among different kinds
of bacteria and remember previous encounters. Its
components are:
1.Mechanical mechanisms: a. skin b. mucous membranes
2. Chemical mediators
3.Cells

4. Immune system
4.Inflammation.
• When the tissue injury occurs either by bacteria or
chemical there is a release of chemical mediators (also
called chemotaxins or chemotactic factor) from infected
area which attract leukocytes especially neutrophils to
the infected area.. The process of attraction is called
chemotaxis.
The chemotaxins produce several effects:
1. Vasodilatation. 2. Increased vascular permeability
resulting in edema 3. “walling off’’ the infected area.

5. Immune system

6. Immune system
• There are two types of inflammation: a. localized b.
systemic.
• Signs and symptoms of inflammation are: heat, redness,
pain, swelling, loss of function and release of chemicals
called pyrogens from leukocytes which cause fever and
inhibit growth of microorganism.
• Pus formation: is dead neutrophil, necrotic tissue, dead
macrophages tissue fluid. A localized collection of pus is
called abscess.
• B- Acquired or adaptive immunity: substances that activate
adaptive immunity are called antigens which are large
molecules with a molecular weight of 10000 or more for
example penicillin.

7. Immune system
• There are two types of antigens:
a. Foreign antigens: Pollen, food, drugs and dried skin.
• Transplanted organs and tissues that contain foreign
antigens result in the rejection of the transplant.
b. Self-antigens: that produced by the body itself. There are
two types of acquired immunity:
1. Humoral immunity. 2. Cellular immunity.
• Humoral immunity: is mediated by B-lymphocytes
which are produce plasma cells. Plasma cells produce
circulating antibodies or immunoglobulins (Ig,s).

8. Immune system
• Humoral immunity can also cause immediate
hypersensitivity reactions such as bronchial asthma.
• Cellular Immunity: is mediated by T-lymphocytes. It is
responsible for delayed allergic reactions (such as
eczema) and rejection of transplants of foreign tissue.
The cytotoxic T cells destroy cells that have the antigen
which activated them. One mechanism by which they
kill is insertion of pore-forming molecules (perforins) in
the membranes of their target cells which leads to
destruction of the cells by osmotic lyses.

9. Immune system
• Immune system problems of clinical significance:
• Hypersensitivity (allergy): is an undesirable side effect of immunity. It
is defined as an inappropriate activation of the body’s immune system
which may result in a very strong inflammation and tissue damage.
Types:
• 1.Immediate hypersensitivity: which is caused by B-cell immunity.
There is reaction between antibodies and antigens. The symptoms
appears within a few minutes of exposure to foreign antigen. For
example, bronchial asthma, food allergies, hay fever.
• 2.Delayed hypersensitivity: mediated by T-lymphocytes and symptoms
take several hours or days to develop. Examples, poison oak, eczema,
soaps, measles, cosmetics, & drugs.
• Q: Write short notes on the allergies in the allergic person. Give
examples.