Immunity and its types

1. IMMUNOLOGY

2. Immunity is body's ability to resist or eliminate
potentially harmful foreign materials or
abnormal cells.

3. • IMMUNITY
• Derived from ‘immunis’- Latin-exempt,
state of protection from infectious
diseases).
• The term immunity refers to the resistance
exhibited by the host towards infections
caused by microorganisms and their
products (toxins).

4. THE MAIN FUNCTIONS OF
IMMUNE SYSTEM – 4 Rs
Recognize pathogen
Respond to it
Remove it
Remember it

5. Healthy immunity accomplishes FOUR essential principles:
(1) ability to detect and fight off infection;
(2) ability to recognize a host's own cells as "self," thereby
protecting them from attack;
(3) a memory from previous foreign infections; and
(4) ability to limit the response after the pathogen has been
removed.

6. • CONSISTS OF FOLLOWING ACTIVITIES:
• Defense against invading pathogens (viruses & bacteria)
• Removal of 'worn-out' cells (e.g., old RBCs) & tissue debris
(e.g., from injury or disease)
• Identification & destruction of abnormal or mutant cells
(primary defense against cancer)
• Rejection of 'foreign' cells (e.g., organ transplant)
• Inappropriate responses:
• Allergies - response to normally harmless substances
Autoimmune diseases

7. DEFINITIONS
 Immunity = resistance of a host to pathogens and their toxic effects
 Immune system = cells, tissues, and organs that mediate resistance
to infections
 Immune response = collective and coordinated response to the
introduction of foreign substances in an individual mediated by the
cells and molecules of the immune system
 Immunology = study of structure and function of the immune
system

8. IMMUNE SYSTEM
ORGANS CELLS MOLECULES
Bone marrow
Thymus
Spleen
Lymph nodes
Payer’s patches
Tonsils and adenoids
Appendix
Lymphatic vessels
Lymphocytes
B-Lymphocytes, plasma cells
T-lymphocytes
natural killer lymphocytes
Monocytes, Macrophage
Granulocytes
neutrophils
eosinophils
Basophils
Antibodies
Complement
Cytokines
Interleukins
Interferons

9. OVERVIEW OF IMMUNE SYSTEN
Immunity
Innate
(Nonspecific)
1o line of
defense
Acquired
(Specific)
2o line of
defense

10. DEFINITIONS
Innate immunity is natural immunity and
inherited along with birth. Eg. Sweat and
tears.
 Acquired immunity is obtained during one’s
life time. It is an adaptation against previous
infection. Eg. Resistance developed after
measles or mumps.

11. THE INNATE IMMUNE SYSTEM
Innate immunity (also called nonspecific or natural immunity)
refers to the inborn-ability of the body to resist, and is genetically
transmitted from one generation to the next. This immunity offers
resistance to any microorganism or foreign material encountered
by the host.
It includes general mechanisms inherited as part of the innate
structure and function of each vertebrate, and acts as first line of
defence. Innate immunity lacks immunological memory, i.e., it
occurs to the same extent each time a microorganism or foreign
material is encountered.

12. FEATURES OF INNATE IMMUNITY
 Acts as first line of defense
 Based on genetic make-up
 Relies on already formed components
 Rapid response: within minutes of infection
 Not specific
 same molecules / cells respond to a range of pathogens
 Has no memory
 same response after repeated exposure
 Does not lead to clonal expansion

13. Mechanism of innate immunity:
1. Anatomical / mechanical / physical barrier
2. Physiological / biochemical barrier
3. Cellular factors / Phagocytic barrier
4. Inflammatory barrier / Inflammation

14. I. ANATOMICAL BARRIERS – PHYSICAL /
MECHANICAL FACTORS
1. Skin 2. mucociliary escalator
3. Flushing action of
saliva, tears and urine
sneezing coughing
vomitting

15. I. ANATOMICAL BARRIERS
1.SKIN- horny outer layer-stratum corneum-impermeable to infectious
microbes. Microbes enter through skin only when skin is damaged.
2.Mucous membrane- line respiratory, gastrointestinal, urogenital
passage prevent the adherence of bacteria to the epithelial cells.
mucus coated nose hairs trap microbes; mucus coated dust or
microbes pushed outward either by sneezing or coughing (speed up
process).
3. cilia- lined respiratory passage-sweep away the mucus trapped
microbes in this passage by their constant movement.

16. I. ANATOMICAL BARRIERS
4. Peristalsis- by constant peristaltic movement the pathogens in the
intestine are pushed away before they could invade and grow there-
vomiting in response to microbial toxins.
5. Tears-lacrimal secretion of the eye -constantly wash over the eye to
flush away the foreign particles.
6. Saliva- constantly washes over teeth and mouth and the pathogens
if any swallowed by the mouth along with salivary secretion.
7. Urine- flushing mechanism prevents colonization of microbes in the
urinary tract.

17. II. Physiological / Biochemical factors
1. Secretion of the skin
2. Secretion of the digestive tract
3. Human milk
4. Nasal secretion and Saliva
5. Lysozyme
6. Interferons
7. Complement
8. Properdin
9. Secretion of bacterial flora
10. Semen
11. Acute phase proteins

19. III. Cellular factors
Natural immunity is provided by 2 cellular factors;
 1. Phagocytosis – phago –eating; cyto- cell
 2. Natural Killer cells (NK cells- non phagocytic)

20. III. Cellular factors

21. III. Cellular factors
 Metchinikoff (1838)- microphage and
 macrophage (big eaters)
 -PMN cells are microphages- neutrophils (in blood),
eosinophils and basophils.
 MN cells- monocytes- macrophages
phagocytosis of microbes (in tissues)-
presentation

23. III. Cellular factors
2. Natural Killer Cells
-non phagocytic with large granules
-originate from lymphoid progenitor along with T and B
cells
-show natural cytotoxicity and they themselves identify a
range of tumour cells and cells infected with viruses
without any antigenic stimulation. So, they named NK cells

24. NK cells choose cells to kill
Some surface proteins are missing

26. Toll-like receptors (TLRs)
• Transmembrane proteins
• Present on macrophages / few other cells
• Conserved across vertebrates
• Important part of innate immune system

27. Toll-like receptors (TLRs)
They look out for microbes (or their components) Bind with microbes or their components

28. What happens when TLR bind to a microbe
TLR binding
to microbe
inflammation
Phagocytosis of
infected cell
Secretion of cytokines/
INF
Apoptosis of
infected cell

29. Cytokines
 Small proteins – secreted by cells of
the immune system
 Affect the behaviour of other cells
 signalling molecules
 Key players in innate and
acquired immunity

30. Which cells release cytokines ?
 Neutrophils – when they encounter a pathogen
 Macrophages – when they encounter a pathogen
 TLRs – bind to microbe / components of a microbe
 NK cells – on encountering a microbe infected cell /tumour cell
 Lymphocytes – when they are activated

31. Examples of cytokines
 Interferons
 Interleukins
 Tumour necrosis factor (TNF)

32. Interferons (IFN)
 Signalling proteins produced by virus infected monocytes and
lymphocytes
 Secreted proteins – Key anti-viral proteins
 “Interfere” with virus replication
 Warn the neighbouring cells that a virus is around...
 If we did not have IFNs – most of us may die of influenza virus infection

33. How does IFN warn the neighbouring cells ?

34. The infected cells release IFN
Antiviral state
Antiviral state
Antiviral state
Antiviral state

35. Virus infects the neighbouring cells
Antiviral state
Antiviral state
Antiviral state

36. Prewarned cells are able to quickly inhibit
the virus

37. Interleukins
 Interleukins – 1-37
 Not stored inside cells
 Quickly synthesized and secreted in response to infection
 Key modulators of behaviour of immune cells
 Mostly secreted by T-lymphocytes & macrophages

38. What to interleukins do ?

39. Tumour necrosis factor (TNF)

44. IV. INFLAMMATION
 Complex biological process by which body
responds to pathogens and irritants
 Associated with swelling of tissue
 Key player in innate immune response

46. Signs of inflammation

47. SIGNS OF INFLAMMATION

48. INFLAMMATION AND INNATE IMMUNITY
Mast cells – similar to basophils in blood;
mast cells are present in tissues and release histamines in response to wound / infection /irritant

50. FEVER
 Inflammatory response is often accompanied by fever.
 Some cytokines stimulate the brain to make
prostaglandins. These prostaglandins stimulate the
hypothalamus to a new temperature set point. The signals
the hypothalamus sends out then:
 Constrict blood vessels in the skin
 Contract skeletal muscles
 Increase heart rate and respiration

51. OTHER FACTORS OR TYPES OF INNATE IMMUNITY
 1. GENETIC FACTORS- Innate immunity is mainly due to
genetic factors thereby differs at the level of species,
races and individuals.

52. Species immunity
Resistance to a pathogen exhibited by all
members of a species.
Eg: Human beings are highly susceptible to
common cold but not dogs.
Rats are insusceptible to diphtheria but humans
are susceptible

53. Racial immunity
 Within a species, different races may show
differences in susceptibility to infections
 Eg: In U.S.A. Negroes are more susceptible to TB
than whites

54. Individual immunity
 The differences in innate immunity shown
by different individuals of the same race .
 Eg: identical twins exhibit similar degrees
of resistance or susceptibility to leprosy
and tuberculosis but not the heterozygous
twins.

55. 2. Body temperature
 Body temperature is also very important in determining innate
immunity.
 Eg: cold blooded animals are not infected with tubercle bacilli
but pathogenic to mammals (warm blooded)
 Hens are naturally immune to anthrax because of its body
temp. of 40°.
 Gonococci are readily killed at the temp. over 40. so, in this
case fever therapy was used earlier before the penicillin .

56. 3. Fever
 A rise in temp. (pyrexia) after
infection is a natural defence
mechanism.
 Accelerates the physiological
processes
 May destroy infectious
pathogens in some cases
 Stimulates the production of INF
and helps to recover from virus
infections

57. THE ACQUIRED IMMUNE SYSTEM
 Acquired immunity is obtained during life time.
 It is an adaptation against previous infection.
 Actually it forms third line of defence
 It is caused by specific antigens

63. Acquired immunity

64. Active Acquired Immunity
Developed as a result of natural infection or vaccination
Involves the synthesis of specific antibodies or production of
immunologically active cells
When the antigen enters the body for the first time, it produces an
immune response called primary immune response. It can produce
memory cells.
When the same antigen enters for the second time it produces
secondary immune response.

66. Natural Active Immunity
Why common cold does not provide us immunity