immunology

1. Definitions in Immunology
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 Immunity is defined as resistance to infectious disease.
 Immune system is the collection of cells and tissues that
protects the body from infection.
 Immune response is the coordinated reaction of the cells
of the immune system to a pathogen.
 Types of Immunity: (A) Innate (B) Adaptive
A. Innate immunity, or nonspecific immunity, is the natural
resistances with which a person is born.
 Innate immunity is a type of general protection.
 Example:
 First line of Nonspecific response: Skin, saliva, mucous
membrane & secretions, normal flora.
 Second line of nonspecific response: phagocytic white
blood cells, complement, antimicrobial substance and
inflammation.

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3. Three Lines of Defense Against Infection
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4. Important components of innate
immunity
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 Phagocytes- Cells that protect the body by ingesting harmful foreign
particles, bacteria, and dead or dying cells.
 -name derived from the Greek word phagein, "to eat" and "-cyte", "cell.
 One litre of human blood contains about 6 billion phagocytes,
 -Phagocytes were discovered in 1882 by Mechnikov.
 Types of Phagocytes white blood cells:
I. Eosinophil: produce histamine: Fight with multicellular parasites,
helminthes
II. Neutrophils: most abundant, 1 litre of human blood contains about 5
billion neutrophils. killed bacteria, constituting 50 to 60% of the total
circulating white blood cells.
III. Basophil: least common of the granulocytes: Involved in Allergic
reactions. Basophils protein receptors binds with IgE.
IV. Mast cells: Have Toll-like receptors, produces cytokines: kill gram-
negative bacteria (e.g., salmonella), and process their antigens.

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V. Monocytes: develop in the bone marrow. Monocytes
differentiated into macrophages or dendritic cells
(a) Dendritic cells: specialized antigen-presenting cells,
 Help to engulf microbes and other invaders.
 Present in the skin, the inner lining of the nose, lungs,
stomach, and intestines.
(b) Macrophages: derive from granulocyte stem cells:
 -contain many lysosomes
 - Secretes interleukin-1, interleukin-6, and TNF-alpha
 -engulf and digest cellular debris, cancer cells, foreign
substances and microbes.
(vii) Natural killer (NK) and lymphokine activated killer (LAK)
cells – NK and LAK cells can nonspecifically kill virus infected and
tumor cells.
(VII) Complement (heat labile serum protein): C3b is an
opsonin, membrane attack complex creates holes in bacterial
membranes
(VIII) Inflammatory response : Limits spread of microbes

6. B. Adaptive Immunity
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 The second kind of protection is adaptive (or active)
immunity, which develops throughout our lives.
 Adaptive immunity involves the lymphocytes and develops
as people are exposed to diseases or immunized against
diseases through vaccination.
 Passive immunity is "borrowed" from another source and it
lasts for a short time.
 For example, antibodies in a mother's breast milk provide a
baby with temporary immunity to diseases the mother has
been exposed to.
 This can help protect the baby against infection during the
early years of childhood. Everyone's immune system is
different.
 Some people never seem to get infections, whereas others
seem to be sick all the time.

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B. Adaptive immunity: is acquired immunity or specific responses
 Third line of specific responses: Lymphocytes, Antibodies
 Lymphocytes: a types of white blood cell in a vertebrate's immune system
 The human body has about 2 trillion lymphocytes, constituting 20–40% of white
blood cells (WBCs)
 T cells (thymus cells) and B cells (bursa-derived cells) are the major cellular
components of the adaptive immune response
(i) B- cells: Humoral mediated immunity: is the type of adaptive immunity
that is mediated by antibodies produced by plasma cells
 (a) Plasma cells- makes antibodies
 (b) Memory cells
(ii) T- cells: Cell- mediated immunity is the type of adaptive immunity
mediated by T lymphocytes.
 (a) Suppressor T- cells
 (b) T- helper cell: secretes cytokines and regulate other immune cells
 (c)T-cytotoxic cells: kill virus infected cells

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9. Comparison between innate and adaptive immunity
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Comparison Innate immunity Adaptive immunity
Response Antigen –independent Antigen –dependent
Time Immediate Lag time
Specificity Not antigen specific Antigen specific
Reaction result No immunologic memory Immunologic memory

10. Organs of the immune system
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 There are several different systems in the human body –
nervous system, blood system, immune system, digestive
system and so on.
 Occasionally, one system can engage in another or there
can be overlapping between them.
 The immune system is composed of different immune
organs, cells and tissues.
 These organs are categorized into two types
1. Primary organs: These are immune organs concerned with
production and maturation of lymphoid cells. Examples Bone
marrow and Thymus gland.
2. Secondary organs: These immune organs are spots or sites
in which the lymphocytes localize, identify unfamiliar antigens
and triggers reaction in opposition to it.
Examples: tonsils, lymph nodes, Spleen, Peyer’s patches (in
the small intestines), appendix

11. (1) Primary organs:
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 (I) Thymus: thymus is a lymphoid gland comprised of two
identically sized lobes, located beneath the breastbone.
Within the thymus T-cells mature.
 Thymocytes: are hematopoietic progenitor cells present in
the thymus.
 Thymopoiesis: is the process in the thymus by which
thymocytes differentiate into mature T lymphocytes.
 -The primary function of thymocytes is the generation of T
lymphocytes (T cells).
 (II) Bone marrow: is the main site of hematopoiesis, the
generation of the cellular elements of blood, including red
blood cells, monocytes, polymorphonuclear leukocytes, and
platelets.
 - The development of B cells occur in the bone marrow.
 -The principal functions of B cells are to make antibodies
against antigens.

12. Secondary organs
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 (I) Lymph node: is an oval-shaped organ of the lymphatic
system, distributed widely throughout the body including the
armpit and stomach and linked by lymphatic vessels.
 -Lymph nodes are major sites of B, T, and other immune cells.
 -There are about 500-700 lymph nodes spread all through our
bodies.
 (II) Spleen: The spleen is an organ found in virtually all
vertebrates.
 - The spleen is responsible for purifying the blood as well as
storing blood cells.
 -It is positioned in the superior abdomen
 -Spleen is the largest lymphatic organ in the body.
 -Spleen contain red and white pulp.
 -Red pulp involve in removing old red blood cells and Mechanical
filtration of red blood cells.
 -White pulp involve in Active immune response through humoral
and cell-mediated pathways.

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14. Antigens (Ags)
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 Antigens: Any substances or foreign particles that induces an
immune response and react with products of that response
are called antigens.
• Epitopes: antigenic determinant sites in the Ags that binds to
Abs.
 Immunogen: a stimulus that produces a humoral or cell-
mediated immune response.
 All immunogens are antigens but not all antigens are
immunogens.
 Immunogens are usually proteins or polysaccharides
 Hapten: a low molecular weight molecule that can be made
immunogenic by conjugation to a suitable carrier.
 Adjuvants: A substance that non-specifically enhances the
immune response to an antigen.
 Characteristics of Ag
1. Immunogenicity: The ability of antigen which can stimulate the
immune system of individual to induce a specific immune
response.

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 _______________is the coordinated reaction of the cells of the immune system to a pathogen.
 First line of Nonspecific response is seen in ________
 Second line of nonspecific response is seen in___________
 Primary organs are concerned with production and maturation of lymphoid cells. Examples are __________ and
_________
 Example of third line of immunity is _____________
 _______________ is the main site of hematopoiesis
 Phagocytes were discovered in 1882 by ___________
 Cells most abundant, 1 litre of human blood contains about 5 billion neutrophils. killed bacteria, constituting 50 to 60%
of the total circulating white blood cells.
 ____________________ are least common of the granulocytes: Involved in Allergic reactions.
 Monocytes: develop in the ______________________.
 Secondary organs are spots or sites in which the lymphocytes localize, identify unfamiliar antigens and triggers
reaction in opposition to it. Examples are ____________ and ____________
 __________________ is an oval-shaped organ of the lymphatic system, distributed widely throughout the body
including the armpit and stomach and linked by lymphatic vessels.
 _______________________a stimulus that produces a humoral or cell-mediated immune response.
 Antibodies are ______________________belonging to the__________________________; the terms antibody and
immunoglobulin are often used interchangeably.
 _______________occur when the immune system of the body responds to its own tissues as if they were foreign.
 What are the types monocytes gets differentited?
 Types of B cells?
 Types of cell mediated immunity
 Types of Hypersensitivity.

16. Antibodies (Abs)
 An antibody (Ab), also known as an immunoglobulin
(Ig), is a large Y-shaped protein produced by B cells.
 Abs is used by the immune system to identify and
neutralize foreign objects such as bacteria and viruses.
 Antibodies are glycoproteins belonging to the
immunoglobulin superfamily; the terms antibody and
immunoglobulin are often used interchangeably.
 Antibodies are secreted by plasma cell.
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18. Immunological disorders
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 An immunological disorder is a dysfunction of the immune
system.
 There are 3 types of immunological disorders
1. Hypersensitivity
2. Autoimmune disease
3. Immunodeficiency
 1. Hypersensitivity: Excessive undesirable
(damaging, discomfort producing and sometimes fatal)
reactions produced by the normal immune system. .
 Hypersensitivity are four types:
 type I:immediate or anaphylactic hypersensitivity
 type II: cytotoxic hypersensitivity
 type III: immune complex reactions
 type IV: cell mediated or delayed type hypersensitivity

19. 2. Immunodeficiency disorders
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 Immunodeficiency is a defect in the immune system that prevents immune
resistance to infectious disease and some forms of cancer.
 There are two types of immunodeficiency:
 Primary immunodeficiency
 Primary immunodeficiencies are hereditary abnormalities characterized by an
inborn defect of the immune system. Example. Severe combined
immunodeficiency (SCID), DiGeorge syndrome, Hyperimmunoglobulin E syndrome
(also known as Job’s Syndrome), Common variable immunodeficiency,
 Secondary immunodeficiency: or acquired immune deficiencies are caused
by something outside the body such as a virus or immune suppressing
drugs. Example
 1. Leukemia,
 2. Hodgkin’s disease,
 3. lymphoma,
 4. Acquired immunodeficiency syndrome (AIDS),
 5. Nephrotic syndrome,
 6. Multiple myeloma,
 7. Sarcoidosis.

20. 3. Autoimmune Diseases
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Autoimmune diseases occur when the immune system
of the body responds to its own tissues as if they were
foreign.
May result from normal reactions to antigens that are
similar, though not identical, to the host’s normal
antigens.
1. Grave’s disease
2. Diabetes mellitus
3. Lupus a
4. Rheumatoid arthritis
5. Myocarditis
6. Addison's disease
7. Thrombocytopenia
8. Hashimoto's encephalopathy

21. Thank You!!
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