1. Introduction To clinical Immunology
Dr. Dalia Galal Hamouda

2. Definition
Immunity: This is a protective or defense mechanism of our body, which leads us to a healthy life.

3. First line of defense Barriers to Entry
The skin is the main barrier preventing the entry of foreign organisms
Skin oils weaken or kill bacteria.
Cilia lining the respiratory tract trapped mucus and particles to the throat to be swallowed
The low pH of the stomach kills microorganisms.
Tears wash the eyes.
Saliva helps clean teeth, preventing dental caries.
Urine flow prevents colonization of the urinary tract.
The normal bacterial colonists of the skin and gut prevent harmful microorganisms from colonizing the areas.

4. Second line of defense Third line of defense
Inborn or innate immunity (non specific):
It is present at birth.
This is our First Line Of Defense.
It is generally effective against a variety of infections. 
Acquired (adaptive) or specific immunity:
It is not present at birth but generally acquired after exposure to the infecting particles or cells.
Specific for one type of  infection
Third line of defense

5. Cells Involved in Immunity
Natural
killer

6. T cells
Denderitic cells
B cells

7. Important components of innate immunity Factors that limit entry of microorganisms into the body
Factor Mode Of Action
-Keratin layer of intact skin Acts as mechanical barrier
-Lysozyme in tears and other secretions -Degrades peptidoglycan in bacteria
cell wall
-Respiratory cilia Elevate mucus containing trapped organisms
-Low pH in stomach and vagina; Retards growth of microbes
fatty acids in skin
-Surface phagocytes Ingest and destroy microbes
(eg. alveolar macrophages)
-Defensins (cationic peptides) Create pores in microbial membrane
-Normal flora of throat, colon Occupy receptors which prevent
and vagina colonization by pathogens

8. Important components of innate immunity Factors that limit growth of microorganisms within the body
Kill virus infected cells
Ingest and destroy microbes
Ingest and destroy microbes, and present antigen to helper T-cells
Inhibit viral replication
C3b is an opsonin, membrane attack complex creates holes in bacterial membranes
Sequester iron required for bacterial growth
Elevated temperature retards bacterial growth
Limits spread of microbes
Causes hypermutation in retroviral DNA and mRNA
Natural killer cells
Neutrophils
Macrophages and dendritic cells
Inferons
Complement
Transferrin and lactoferrin
Fever
Inflammatory response
APOBEC3G (apolypoprotein is RNA editing enzyme)

9. Important components of adaptive immunity
B Lymphocytes and T lymphocytes
B lymphocytes (B cells) mature in the bone marrow.
B lymphocytes have receptors (antibodies) attached to their surface which function to detect antigens.
There is only one specific kind of receptor on the surface of a lymphocyte. A single B lymphocyte can therefore detect only one kind of antigen. Our bodies have millions of different kinds of B lymphocytes.
T lymphocytes (T-cells) are lymphocytes that mature in the thymus.
This type of immunity is used to fight cells such as cancer cells, virus-infected cells, single-celled fungi, parasites, and cells of an organ transplant.

10. B cells
T cells

11. Major Functions Of T Cells and B cells
Cell Mediated Immunity
1) Host defense against infection (especially M.tuberculosis, fungi and virus infected cells)
2) Allergy (hypersensitivity )eg poison oak
3) Graft and tumor rejection
4) Regulation of antibody response (help and suppression)
Antibody-Mediated Immunity (B Cells)
1) Host defense against infection
2) (Opsonize bacteria, neutralize toxins and viruses)
3) Allergy (hypersensitivity) eg, hay fever anaphylactic shock
4) Autoimmunity

12. Antigens and Antibodies
Antigens are molecules that stimulate antibodies which are capable of being recognized. They are usually a protein or carbohydrate chain. The body can recognize bacteria and viruses as being foreign because they have antigens on their surface which are different than the bodies "self" antigens.
Antibodies are proteins that protect against foreign invaders, either foreign molecules, viruses, or cells. Antibodies are produced by B lymphocytes. .
Antibodies are Y-shaped molecules with a constant region and two binding sites that vary from one antibody to the next.
Antibodies fit together with and bind with antigens like a lock and key.
The body does not produce antibodies that bind to its own (self) antigens. But bound to foreign antigens.

13. Cells, particles, or molecules that are marked with antibodies:
may be phagocytized (engulfed) by neutrophils or macrophages.
2. may agglutinate (clump together) because each antibody is capable of binding to two antigens. If the antigens are chemicals that are dissolved in the body fluids, the clumps of antibody-bound particles will precipitate. Antigens attached to cells will cause the cells to clump together. The clumps are then phagocytized.
3. may activate the complement system. The complement system is a system of blood proteins that enhances the elimination of foreign cells or particles.
During our life, we will encounter over 1 million different antigens, so we need at least 1 million different antibodies, one for each kind of antigen.
There are 5 different classes of antibodies (IgA, IgD, IgG, IgH, IgM). One class contains pentamers, another contains dimers.

15. Important features Of Innate and Acquired (adaptive) Immunity
Type of Immunity Specificity Effective immediately Improves Has
after exposure to After Exposure memory
microbe
Innate Nonspecific Yes in No No
minutes
Acquired Highly No--requires Yes Yes
specific several days
before becoming
effective

16. Organs of the Immune System
1. Primary lymphoid organs
Bone Marrow
Largest tissue of the body
Main source of hematopoietic cells.
Lymphocyte stem cells released from marrow and travel to primary lymphoid organs for maturation: T cells go to Thymus, B cells mature in bone marrow.
Thymus
Ductless gland-like structure located beneath the sternum (breastbone).
Lymphocyte stem cells develop into T lymphocytes under the influence of thymic hormones.

17. 2. Secondary lymphoid tissue
From the primary lymphoid organs, B and T lymphocytes migrate to the peripheral secondary lymphoid organs.
1) They encounter antigens and are transformed into an activated state.
2) They become effectors of the humoral or cell-mediated immunity.
Spleen
It is the body's largest reservoir of mononuclear-phagocytic cells.
Both T and B lymphocytes are present but they are segregated.
The red pulp of the spleen consists of blood vessels lined with macrophages.
White pulp contains lymphoid tissue.
Also functions as a filter by removing effete cells from circulation.
Lymph nodes
Located in several areas of the body, including the neck and those points where the arms and legs join the trunk of the body.
They serve as a filter for the tissue fluid or lymph.
Lymph is a collection of tissue fluid flowing from the limbs and tissues through the lymph nodes on its way to the blood stream.

18. Examples of other Secondary Lymphoid Tissue or organs
Gut associated lymphoid tissue
Tonsils
Bronchus associated lymphoid tissue
Mammary glands
Salivary glands

20. Overview of the Immune Response