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1. Introduction
The immune system is:
Defense body mechanism
an interacting set of specialized cells and
proteins designed to identify and destroy
foreign invader

2. Introduction
The immune system must be able to:
differentiate between material that is
a normal component of the body
(“self”) and material that is not
native to the body “nonself”
A highly specialized receptors present
for discriminating between ”self” and
“nonself” body components

3. Introduction
*The discrimination between “self” and “non-self” and the
subsequent destruction and removal of foreign material
is accomplished by the two arms of the immune system
1) The innate (natural or nonspecific) immune system
2) The adaptive (acquired or specific) immune system
*These two systems perform many of their functions by
cooperative interactions

4. Immunity
Innate immunity Adaptive immunity
Humeral Cell-mediated
Components Components
Macrophages antigen presenting cells
Granulocytes T-cells
Natural killer cells B-cells
Complement Antibodies
Other chemicals: HCL, lysozyme Complement
Characteristics Characteristics
* Action is immediate * Action requires days to develop
* Response is non-specific * Response is specific
* Response is not enhanced on * Response is enhanced on
repeated exposure to pathogen repeated exposure to pathogen

5. Overview of the innate immune system
* It is the first line of defense
* It is active at the time of infection
• It consists of:
a- protective cellular (WBCs and derivatives)
b- chemical components

6. The response of the innate immune system
It is divided into two stages:
1- non-inflammatory reaction (body’s static defenses)
skin, gastric pH, lysozyme in tears, saliva, mucous
2- local inflammation promotes migration of phagocytes
and plasma protein into infected tissues
The phagocytes respond to surface structures present
in large groups of microorganisms (peptidogcan,
mannose)

7. Role of external body surfaces
* The skin consists of sheets of dry, cornified
epithelial cells
Intact skin act as barrier to bacteria and viruses
* Hair follicles and sebaceous glands produce:
Antibacterial substances (fatty acids and
enzymes)
* Normal microbial flora compete with:
potential pathogens

8. Role of internal body surfaces
The normal movement of fluids and mucous act as
mechanical factors for cleaning internal surfaces of:
Respiratory tract
Gastrointestinal tract
Genitourinary tract

9. Acute Inflammation Resulting From Infection
Inflammation is a nonspecific response of
living tissue to localize and eliminate
the injurious agent
The injury may be:
physical, chemical or biological

10. The Inflammatory Response
Specialized cells and serum proteins
move from plasma to interstitial spaces
to provide an immediate defense

11. The Inflammatory Response
The inflammatory cells include:
- Phagocytes which destroy the invading
organisms by phagcytosis followed by
intracellular digestion
- Natural killer cells which limit infection by
releasing compounds toxic to organisms

12. The Inflammatory Response
* Serum components:
Acute phase proteins (e.g. C-reactive protein)
- C-reactive protein is produced by liver in
response to tissue damage
- C-reactive protein binds to the cell walls of
bacteria and activates the complement
system resulting in the opsonization and
lyses of pathogenic organisms

13. Role of Phagocytosis
1- Chemotaxis & attachment
a- Attraction by chemotact. Subst. ( microbes,inflam. tissues)
b- Attachment by receptors on surfaces of phagocytes
2- Ingestion
* Phag. pseudopodia surround organism forming phagosom
* Opsinins and co factors enhance phagocytosis
* Fusion with phag. granules and release digestive ,toxic contents
3- Killing (two microbicidal routes)
a- Oxygen depended system (powerful microbicidal agents)
Oxygen converted to superoxide, anion, hydrogen peroxide,
activated oxygen and hydroxyl radicals.
b- Oxygen-independent system (anaerobic conditions)
Digestion and killing by lysozyme. Lactoferrin, low pH,
cationic proteins and hydrolytic and proteolytic enzymes

14. Innate Immunity

15. Innate Immunity
Defensive mechanisms include :
1) Innate immunity (Natural or Non specific)
2) Acquired immunity (Adaptive or Specific)
Cell-mediated immunity Humoral
immunity

16. Component of Innate Immunity
Innate Immune system
First line Second line
1) Mechanical barriers A- cells
2) Chemical & biochemical inhibitors 1- Natural killer
3) Normal flora 2- Phagocytes
B- Soluble factors
C- Inflammatory barriers

17. First line
1) Mechanical barriers
- Intact skin
- Mucous coat
- Mucous secretion
- Blinking reflex and tears
- The hair at the nares
- Coughing and sneezing reflex

18. First line
2) Chemical & biochemical inhibitors
- Sweat and sebaceous secretion
- Hydrolytic enzymes in saliva
- HCl of the stomach
- Proteolytic enzyme in small intestine
- Lysozyme in tears
- Acidic pH in the adult vagina

19. First line
3) Normal bacterial flora
- Competition for essential
nutrients
- Production of inhibitory
substances

20. Second line
A) cells
1- Natural killer (NK)
Definition: Large granular lymphocytes
Innate cytotoxic lymphocytes
Source : Bon marrow precursors
Location : 10% or 15% of lymphocytes in peripheral blood
1% or 2% of lymphocytes in spleen
Tumor cells
Function : Cytotoxic for Viral infected cells
Bacterial, fungal, parasitic infection
Responsible for antibody–dependent cell
mediated cytotoxicity (ADCC)

21. Second line
2- Phagocytes
Specialized cells for capture, Ingestion and destruction
of invading microorganisms
* Polymorphonuclear leucocytes, mainly neutrophils:
granulocytes circulate in blood
* Mononuclear cells (macrophages)
- Monocytes in blood
- Histocytes in connective tissues
- Fixed reticuloendothelial cells in liver spleen,
lymph nodes, bone marrow

22. Second line
B- Soluble factors
1- Acute phase protein (Plasma protein, CRP=C
reactive protein, Fibrin.)
2- Complement (proteins in serum, body fluids)
2- Interferons (Proteins against viral infections)
3- Properdin (Complement activation)
4- Beta lysine(Antibacterial protein from
Platelets)
5- Lactoferrrin,Transferrin (Iron binding protein)
6- Lactoperoxidase (Saliva & Milk)
7- Lysozyme (Hydrolyze cell wall)

23. Interferons
Proteins usually produced by virally infected cells
* Types of interferons:
1- Alpha interferon Secreted by Macrophages
Induced by Viruses or Polynucleotide
2- Beta interferon Secreted by Fibroblasts, Viruses
3- Gamma interferon T- lymphocytes, Specific antigens

24. Interferons
Protective action of interferons:
1) Activate T-cells
2) Activate macrophages
3) Activate NK

25. Phagocytosis
The engulfment, digestion, and subsequent
processing of microorganisms by macrophages
and neutrophils
1) Chemotaxis & attachment:
a- Attraction by chemotactic substances
(microbes, damaged tissues)
b- Attachment by receptors on surfaces of
phagocytes

26. Phagocytosis
2) Ingestion:
* Phagocyte pseudopodia surround
organism forming phagosome
* Opsinins and co-factors enhance
phagocytosis
* Fusion with phagocyte granules and
release digestive, toxic contents

28. Phagocytosis
3- Killing (two microbicidal routes)
a- Oxygen depended system (powerful microbicidal
agents) Oxygen converted to superoxide, anion,
hydrogen peroxide, activated oxygen and hydroxyl
radicals.
b- Oxygen-independent system (anaerobic
conditions) Digestion and killing by lysozyme.
Lactoferrin, low pH, cationic proteins and hydrolytic
and proteolytic enzymes

29. C) Inflammatory Barriers
* Tissue damage by a wound or by invading pathogen
* Inflammatory response:
Tissue damage
Release of chemical mediators from Leukocytes
(Histamine, fibrin, kinins, cytokines) Invading microbe
Redness of tissue
Tissue temperature
Vasodilatation of capillaries Capillary permeability
Influx of fluids
Influx of phagocytes
into tissues

31. Acquired Immunity

32. Acquired (Adaptive) Immunity
Defensive mechanisms include :
1) Innate immunity (Natural or Non specific)
2) Acquired immunity (Adaptive or Specific)
Cell-mediated immunity Humoral immunity

33. Acquired (specific) immunity
* The acquired immune response is more specialized than
innate immune response
* The acquired immune response involves a combination
of two mechanisms :
1) Humoral immune response
2) cell mediated immune response
* They interact with one another to destroy foreign body
(microorganisms, infected cells, tumor cells)

34. Acquired (specific) immunity
Two mechanisms
1) Humoral immune response:
- Antibodies are produced by B-lymphocytes
- These have the ability to recognize and bind
specifically to antigen that induced their formation
2) The cell mediated immune response (CMI)
- It is mediated by certain types of T-
lymphocytes
- T-lymphocytes recognize foreign material by
means of surface receptors
- T-lymphocytes attack and destroy foreign
material directly or through release of soluble
mediators i.e. cytokines

35. Characters Of Acquired Immune Response
1) Highly specific for the invading organism
2) Discrimination between “self and “non self” molecules
The response only occurs to “non self” molecules
3) Diversity:
- It can respond to millions of different antigens
- Lymphocytes population consists of many different
clones (one cell and its progeny)
- Each clone express an antigen receptor and
responds only to one antigenic epitope

36. Mechanism Of Acquired Immune Response
Acquired immune response is initiated by:
* Recognition of the antigen by specific lymphocytes
* Activation of these specific lymphocytes
* Proliferation and differentiation into effector cells;
-The effector cells eliminate the antigen
-Return of homeostasis and development of memory cells
* Memory cells evoke a more rapid and long response on
re-exposure to same antigen

37. Acquired Or Adaptive Immunity
I- Passive acquired immunity
a-Naturally passive acquired immunity
Antibodies are passed through placenta to
the fetus
b- Artificially passive acquired immunity
The injection of ready prepared antibodies,
such as gamma globulin (short-term
immunization)

38. II- Active acquired immunity
a-Natural active acquired immunity :
- Following clinical or subclinical infections
- measles or mumps, in which immunity is
long lasting
b- Artificial active acquired immunity :
- Following vaccination with live or killed
infectious agents or their products

39. Mechanism of Humoral immunity
• Antibodies induce resistance through:
• Antitoxin neutralize bacterial toxins (diphtheria, tetanus)
Antitoxin are developed actively as a result of:
a- Previous infection
b- Artificial immunization
c- Transferred passively as antiserum
* Neutralization of toxin with antitoxin prevents a
combination with tissue cells

40. Mechanism of Humoral immunity
2) Antibodies attach to the surface of bacteria and
a- act as opsonins and enhance phagocytosis
b- prevent the adherence of microorganisms to
their target cells, e.g. IgA in the gut
c- Activate the complement and lead to bacterial lysis
d- Clump bacteria (agglutination) leading to
phagocytosis

41. Vaccination
* Vaccination prevents and control such diseases as
cholera, rabies, poliomyelitis, diphtheria, tetanus,
measles, and typhoid fever
* Vaccines can be:
a- prophylactic (e.g. to prevent the effects of
a future infection by any natural or "wild"
pathogen
b- Therapeupic (e.g. vaccines against cancer
are also being investigated)

42. Vaccination
Vaccination:
*Producing immunity against pathogens
(viruses and bacteria) by the introduction of
live, killed, or altered antigens that stimulate
the body to produce antibodies against more
dangerous forms
*Vaccines work with the immune system's
ability to recognize and destroy foreign
proteins (antigens)

43. Vaccination
Immunization of young children and adolescents:
- Hepatitis B (HepB) and Hepatitis A (HepA)
- Diphtheria, tetanus and pertussis (whooping cough)
given together as DTaP (formerly DTP)
- Haemophilus influenzae b (Hib)
- Poliomyelitis (IPV)
- Measles, Mumps, and Rubella, given together as MMR
- Chicken pox (Var)
- Neisseria meningitidis (meningococcal meningitis)