immunity studies

1. IMMUNITY(HOST DEFENCES)
Dr. Bangar Raju

2. Immunity = Immunis (Latin) = Free from burden
Defn: State of resistance exhibited by the host to
toxic molecules, microorganisms and foreign
cells
This resistance plays a major role in warding
off infectious diseases
Carried out by the process of recognition and
disposal of non-self or foreign material that
enters the body
Susceptibility- lack of resistance

3. Immunity
Innate/natural Adaptive/Acquired
immunity immunity
(Non specific) (Specific)

4. INNATE IMMUNITY
Resistance which individual possesses by birth
by virtue of his genetic or constitutional make
up
All normal healthy individuals are borne with
innate defence mechanisms
It comprises of non specific general
mechanisms acting as barriers against
frequently encountered pathogens

5. TYPES OF INNATE IMMUNITY
 Species Immunity: Resistance shown by all
members of a particular species
 Racial Immunity: Different races within one species
exhibiting differences in resistance to infections
 Individual Immunity: Resistance to infection varies
with different individuals of same race and species
FACTORS INFLUENZING INNATE
IMMUNITY
 Age
 Hormones
 Nutrition

6. MECHANISMS OF INNATE IMMUNITY
3 types of general mechanisms
Anatomical factors
 Mechanical factors
 Chemical factors
 Biological factors
Cellular factors
Humoral factors

7. ANATOMICAL FACTORS
The epithelial surfaces form a physical barrier
that is very impermeable to most infectious
agents
SKIN
 Intact ,unbroken skin- mechanical covering
 Multilayered structure
 Keratinized cells- hardened , protective barrier
 Desquamation
 Sebaceous glands- sebum fatty acids acid
pH
 Sweat glands  sweat – high salt
concentration-lethal to many bacteria.

8. NOSE, NASOPHARYNX AND RESPIRATORY
TRACT
 Mucus secretions- traps the organisms
 Hair like cilia- propels out the microbes
 Cough reflex-drives out the particles
 Alveolar macrophages- phagocytose the
organisms reaching the alveoli.

10. EYES
 Eye lids, eye lashes- mechanical
protection
 Conjunctiva- coated with mucus
 Tear glands – secrete tears – flushing
action
 Tears- lysozyme- bactericidal
It lyses the cell wall of bacteria

11. “Both tears and sweat are salty, but they
render a different result. Tears will get you
sympathy; sweat will get you change.”
Jesse Jackson
BUT I SAY THAT BOTH WILL MAKE
YOU IMMUNE!!

12. EAR
 Auditory canal lined with ciliated epithelium
 Ceruminous glands secrete cerumin/wax
 Traps microorganisms- moves out away from middle
ear due to beating action of cilia
 Eardrum- mechanical barrier
DIGESTIVE TRACT:
Lined with mucus memb. coated with mucus
Oral cavity- saliva- mild bactericidal action
Stomach- Gastric acid- Hcl- lethal to microbes
Gall bladder- Bile Salts- inhibits bacteria
Colon- diverse normal flora- produce substances called
bacteriocins
Inhibit growth of potential pathogens
Colonization resistance

13. URINARY TRACT
Flushing action of urine
Sphincter muscle – mechanical barrier
Urine- Acid pH - 4.5-5.0
REPRODUCTIVE SYSTEM:
 Male :semen- antibacterial substances
 Female : vagina lined with mucus membranes
Acidic pH due to fermenting action of
lactobacillus

14. Downloaded from: StudentConsult (on 15 July 2008 10:01 AM)
© 2005 Elsevier

15. CELLULAR FACTORS
The cells
Phagocytosis and intracellular killing
Inflammation

16. CELL FUNCTIONS
NEUTROPHIL •Phagocytosis and intracellular killing
•Inflammation and tissue damage
MACROPHAGE •Phagocytosis and intracellular killing
•Extracellular killing of infected or altered self targets
•Tissue repair
•Antigen presentation for specific immune response
NK AND LAK
CELLS
•Killing of virus-infected and altered self targets,
tumor cells
EOSINOPHIL •Killing of certain parasites

17. NEUTROPHILS

18. MACROPHAGE & NEUTROPHILS

19. ALVEOLAR MACROPHAGE

20. Downloaded from: StudentConsult (on 16 July 2008 11:07 AM)
© 2005 Elsevier

21. EOSINOPHIL

22. PHAGOCYTOSIS
• Attachment
•Pseudopod extension
•Phagosome formation
•Granule fusion
•Phagolysosome formation

23. Downloaded from: StudentConsult (on 15 July 2008 10:09 AM)
© 2005 Elsevier

25. INTRACELLULAR KILLING PATHWAYS
BY PHAGOCYTES
Intracellular Killing
Oxygen Dependent
(Respiratory burst)
Oxygen Independent
lysozyme
Cathepsin
lactoferrin
Hypochlorus acid
Singlet oxygen
Superoxide anion
Hydrogen peroxide

26. INFLAMMATION
Generalized response following any type
cell injury- trauma, chemical agents,
physical agents, invasion by microbes
Occurs as a result of
Release of various mediators
Increased blood flow
Aggregation of micro & macrophages by
chemotactic mechanisms

28. FUNCTIONS:
1.Destroy and /or remove injurious agent
2. Limits spread of injurious agent
3. Repair or replace injured tissues
CLINICAL FEATURES

29. HUMORAL BARRIERS
Non specific antibacterial substances in
blood and tissue
Includes
• Complement system
• Interferons
• Acute phase proteins
• Defensins

30. COMPLEMENT SYSTEM
A system of series of serum proteins involved
in immunity
When activated, these proteins react in a
specific series of overlapping reactions
(complement cascade)
• Results in lysis of cell membrane
• ↑ phagocytosis
• Inflammation

32. Downloaded from: StudentConsult (on 15 July 2008 10:09 AM)
© 2005 Elsevier

33. INTERFERONS
Group of soluble proteins in plasma
Antiviral
Types- α interferon, β interferon, γ interferon
Produced by WBCs, fibroblasts, T-lymphocytes
Produced only after viral penetration
Viral specific- acts against viruses only
Non specific in action- effective against wide
variety of viruses
Aspirin inhibits interferon production Ryes
syndrome

34. Downloaded from: StudentConsult (on 15 July 2008 10:09 AM)
© 2005 Elsevier

35. DEFENSINS
Important component of innate immunity
Highly positively charged (cationic) peptides
Create pores in bacterial membrane thereby
killing them
Located primarily in GIT and lower respiratory
tract
Types: alpha and beta defensins
Alpha defensins: GIT
Beta defensins: Lower resp tract

36. ACUTE PHASE PROTEINS
Normal serum proteins- synthesized in liver
Levels increase markedly in inflammation,
infection, trauma
Helps in innate immunity
Common examples
C- reactive protein
Alpha-1 antitrypsin
Haptoglobin
Ceruloplasmin

37. FEVER
 Protective defense mechanism of the body
 Increase in body temperature
 inhibits growth of most viruses & some bacteria
 increase metabolic reactions in host cells
 ses blood circulation and flushing of tissues that help
to eliminate toxin thro’ urine & sweat
 Stimulates the prodn of interferons- recovery from viral
infections
 Controlled by hypothalamus
 Activated by pyrogens - released by microbes, injured
host cells

39. ACQUIRED IMMUNITY
The resistance acquired by an individual during his life
AQUIRED IMMUNITY
Active passive
Active immunity
Resistance induced in an individual after effective
contact with antigen
Active participation of one’s immune system in the
production of antibody & cell mediated immunity
Develops slowly over a period of days and weeks
Persists for a long time, usually for years

40. ACTIVE IMMUNITY
Natural Active Artificial active
Through clinical or Thro’ vaccination
subclinical infections

Eg:-persons recovering
from small pox infection

41. VACCINATION
The vaccines are preparations of live attenuated or killed
microorganisms, or their antigens, or active materials
derived from them

42. VACCINES
INACTIVATED ( KILLED) VACCINES:
Inactivated/ killed organisms
Killed by formalin, phenol, alcohol etc
Eg: Bacterial- TAB vaccine for typhoid fever
Viral- Salk vaccine for poliomyelitis
LIVE ATTENUATED VACCINES:
Live attenuated organisms
Attenuation done by ageing of culture, drying,
passage thro’ animals of different species etc
Eg: Bacterial- BCG, Anthrax, plague, brucella
vaccines
Viral- MMR, Polio (sabin), Smallpox

43. TOXOIDS
Inactivated bacterial exotoxins
Retain immunogenicity, but loose toxigenicity
eg: tetanus toxoid, diphtheria toxoid

44. ANTIGENIC PREPARATIONS
extracted from organism, genetically
engineered
Eg: Capsular Ag of Strep. pneumoniae,
Genetically engineered protein-
Hepatitis B

45. PASSIVE IMMUNITY
Resistance that is induced in the recipient by
transfer of preformed (readymade) antibodies
against infective agent or toxin in another host
No active role for immune system
Immediate effect
Protection short lasting only for days or weeks

46. Passive immunity
NATURAL ARTIFICIAL
Placental
transfer of IgG
(from mother to
fetus)
Readymade
Antibodies or
immunoglobulins
Colostral
transfer of IgA(
from mother to
infant)
Immune cells

48. ARTIFICIAL PASSIVE IMMUNITY
 Useful where instant immunity is required
when faced with the threat of a serious infection
Agents used:
Hyper immune sera of animal or human origin
Eg:- Diphtheria, tetanus, gas gangrene, rabies
Convalescent sera
Pooled human gamma
globulins

49. Vaccination as such will be dealt in detail in
another class!!!!

50. Non specific immunity
(INNATE IMMUNITY)
Response is antigen
independent
 Immediate maximal
response
No immunological
memory
Specific immunity
(AQUIRED IMMUNIT
Response is antigen
dependant
A lag time between
exposure and
maximum response
Immunological mem
present

51. Immunity
Natural/Innate Acquired
Mechanical factors
Cellular factors
Humoral factors
Active Passive
Natural Artificial Natural Artificial
Clinical or Vaccination Mother to Readymade
Subclinical inf fetus Abs

52. REFERENCES
Warren Levinson’s review of medical
microbiology and immunology- 9nth edition
Javetz’s medical microbiology- 24th
edition
Cedric Mims’ Medical microbiology- 4th
edition