4. Mechanisms of Disease by Pathogens
• Utilization of host nutritional resources
• Physical damage to host tissues
• Production of toxic substances
• Chromosomal and gene damage
• Body cells behave abnormally
6. • Skin acts as barrier to microbes and viruses
- sweat has a low pH
• Mucus traps foreign particles
• Tears
- Lysozyme has antimicrobial action
• Gastric stomach acid
1st Line of Defense
14. Immunity:
• The state of being immune from or insusceptible to a particular
disease.
• The condition that permits either natural or acquired
resistance to disease.
• The ability of the cell to react immunologically in the presence
of antigen.
15. How immunity develops
• During the body’s first encounter with a pathogen there
will be few lymphocytes with specific receptors
• It takes time to divide to form clones, B lymphocytes to
secrete antibodies, T lymphocyte production
• If the same pathogen invades again persisting memory
cells can give a faster, more effective response
16. Characteristics of Immunity
• Recognition of self versus non-self
• Response is specific
• Retains a “memory” allowing an accelerated second response
• Can respond to many different materials
• Involves lymphocytes and antibodies
17. Types of Immunity
• Active Immunity
- Naturally-Acquired Active Immunity
- Artificially-Acquired Active Immunity
• Passive Immunity
- Naturally-Acquired Passive Immunity
- Artificially-Acquired Passive Immunity
19. • An infection is an example of acquiring natural
immunity. It is called ACTIVE as your body needs to
work to produce the necessary antibodies
• When a mother breast feeds her baby she passes
antibodies to it. This is a way of acquiring PASSIVE
immunity as it is a way of gaining antibodies without
the immune system having to produce them.
• The thick, yellowish milk (colostrum) that is produced
for the first few days after birth is particularly rich in
antibodies.
Natural immunity: active and passive
20. Artificial immunity: active and passive
• An alternative to natural immunity
developing is to give vaccinations
(artificial immunity)
• Antigen is injected into the body.
• This may be in the form of an
inactivated bacterial toxin or
attenuated (not harmful) virus which
would promote ACTIVE immunity;
• or the injection of antibodies or
antitoxins which would promote
PASSIVE immunity (eg Clostridium
tetani)
21. • The production of antibodies against a specific disease by the
immune system.
• Naturally acquired through disease
• Artificially acquired through vaccination
• Vaccines include inactivated toxins, killed microbes, parts of
microbes, and viable but weakened microbes.
• Memory cells are only produced in active immunity.
• Protection for active immunity is permanent whereas in
passive immunity it is only temporary.
• Antigens are only encountered in active immunity.
• Active immunity takes several weeks to become active but
passive is immediate
Active Immunity
22. • A vaccinated person has a secondary response based on
memory cells when encountering the specific pathogen.
• Routine immunization against infectious diseases such as measles
and whooping cough, and has led to the eradication of smallpox, a
viral disease.
• Unfortunately, not all infectious agents are easily managed by
vaccination.
• HIV vaccine in the works
23. • Passive Immunity- Protection against disease through
antibodies produced by another human being or animal.
• Ex. Maternal antibodies , Colostrum
• Passive immunity doesn’t last as long as active immunity (only
weeks or months):
• No lymphocytes are stimulated to clone themselves
• No memory cells have been made
• Effective, but temporary as this type of immunity can only last
as long as the antibodies/toxins last in the blood
Passive Immunity
24. • Passive immunity can be transferred artificially by injecting
antibodies from an animal that is already immune to a
disease into another animal.
• Rabies treatment: injection with antibodies against rabies virus that are
both passive immunizations (the immediate fight) and active
immunizations (longer term defense).
25. Immune System Response toAntigens
A. Humoral Immunity
• Involves antibodies (secreted from B cells) dissolved in the
blood plasma.
• Demonstrated as a immune response using only the blood
serum.
• Defense against bacteria, bacterial toxins, & viruses.
B. Cell-Mediated Immunity
• Involves the activities of specific white blood cells (T cells).
• Defense against cancer cells, virus-infected cells, fungi,
animal parasites, & foreign cells from transplants.
27. B Cells
• Mature in bone marrow
• Involved in humoral immunity
• Once activated by antigen,
proliferate into two types of clones
• Plasma cells
that secrete antibodies and
• memory cells
that may be converted into plasma
cells at a later time
32. T Cells
• Mature in thymus
• Involved in cell-mediated immunity
• Activated when another cell presents antigen to
them
• Several types of T cells:
• cytoxic T cells,
• helper T cells,
• suppressor T cells,
• memory T cells
33. • There are two main types of T cells, and each
responds to one class of MHC molecule.
– Cytotoxic T cells (TC) have antigen receptors that
bind to protein fragments displayed by the body’s
class I MHC molecules.
– Helper T cells (TH) have receptors that bind to
peptides displayed by the body’s class II MHC
molecules.
T Cells
37. Humoral Immune Response
time (days)
antibody
concentration
first exposure
to antigen A
primary response:
concentration of
anti-A antibody
second exposure to
antigen A
38. Humoral Immune Response
time (days)
antibody
concentration
secondary response:
concentration of anti-A
antibody
second exposure to
antigen A
first exposure
to antigen B
39. Humoral Immune Response
time (days)
antibody
concentration
primary response:
concentration of
anti-B antibody
first exposure
to antigen B
40. • Antibodies constitute a group of globular serum proteins
called immunoglobins (Igs).
• A typical antibody molecule has two identical antigen-binding sites
specific for the epitope that provokes its production.
Antibody
Molecule
antigen binding sites
antigen
light chains heavy chains
41. Mechanisms on Antibody Action
• Precipitation of soluble antigens
• Agglutination of foreign cells
• Neutralization
• Enhanced phagocytosis
• Complement activation leading to cell lysis
• Stimulates inflammation
The binding of antibodies to antigens to form antigen-antibody
complexes is the basis of several antigen disposal mechanisms
45. • Malfunctions of the immune system can produce effects
ranging from the minor inconvenience of some allergies to
the serious and often fatal consequences of certain
autoimmune and immunodeficiency diseases.
Abnormal immune function can lead
to disease
Abnormal Immune Function
• Autoimmune Disease
• Allergy
• Immunodeficiency
47. Vaccination
• Vaccination is a method of giving antigen to stimulate the immune
response through active immunization.
• A vaccine is an immuno-biological substance designed to produce
specific protection against a given disease.
• A vaccine is “antigenic” but not “pathogenic”.
One of the most effective «weapons» in medicine
1798 Edward Jenner immunizes first time against smallpox
1885 Louis Pasteur prepares the 1st vaccine against Rabbies
1927 BCG (bacillus Galmette-Guerin)
1955 Salk vaccine against poliomyelitis
1960 MMR (Measles, Mumps and Rubella)……..
48. Types of vaccines
• Live vaccines
• Attenuated live vaccines
• Inactivated (killed vaccines)
• Toxoids
• Polysaccharide and polypeptide
(cellular fraction) vaccines
• Surface antigen (recombinant) vaccines
49. Live vaccines
• Live vaccines are made from live infectious
agents without any amendment.
• The only live vaccine is “Variola” small pox
vaccine, made of live vaccinia cow-pox virus
(not variola virus) which is not pathogenic but
antigenic, giving cross immunity for variola.
50. Live attenuated (avirulent) vaccines
• Virulent pathogenic organisms are treated to become
attenuated and avirulent but antigenic. They have lost
their capacity to induce full-blown disease but retain
their immunogenicity.
• Attenuated– live microbe (usually virus) which has a
vital function inactivated by heat, chemicals or genetic
manipulation e.g. Rabies virus vaccine, MMR
(Measles, Mumps and Rubella), BCG (Bacillus
Calmette Guerin vaccine for M. tuberculosis
• Risk it could revert back to infectious agent
• will stimulate both cell mediated and antibody
mediated immune response
51. Live attenuated (avirulent) vaccines contd..
Live attenuated vaccines should not be administered to
persons with suppressed immune response due to:
• Leukemia and lymphoma
• Other malignancies
• Receiving corticosteroids and anti-metabolic
agents
• Radiation
• pregnancy
52. Inactivated (killed) vaccines
• Organisms are killed or inactivated by heat or
chemicals but remain antigenic.
• They are usually safe but less effective than live
attenuated vaccines.
• The only absolute contraindication to their
administration is a severe local or general reaction to a
previous dose
53. Toxoids
• They are prepared by detoxifying the exotoxins of
some bacteria rendering them antigenic but not
pathogenic.
• Adjuvant (e.g. alum precipitation) is used to increase
the potency of vaccine.
• The antibodies produces in the body as a consequence
of toxoid administration neutralize the toxic moiety
produced during infection rather than act upon the
organism itself.
• In general toxoids are highly efficacious and safe
immunizing agents.
54. Polysaccharide and polypeptide vaccines
• They are prepared from extracted cellular fractions e.g.
meningococcal vaccine from the polysaccharide
antigen of the cell wall, the pneumococcal vaccine
from the polysaccharide contained in the capsule of the
organism, and hepatitis B polypeptide vaccine.
• Their efficacy and safety appear to be high.
55. Surface antigen (recombinant) vaccines
• It is prepared by cloning HBsAg gene in yeast cells
where it is expressed.
• HBsAg produced is then used for vaccine preparations.
• Their efficacy and safety also appear to be high.
58. Scheme of immunization
• Primary vaccination
• One dose vaccines (BCG, variola, measles, mumps, rubella, yellow fever)
• Multiple dose vaccines (polio, DPT (diphtheria, pertussis, tetanus toxoids),
hepatitis B)
• Booster vaccination
To maintain immunity level after it declines after some time has elapsed (DT,
MMR).
59. Periods of maintained immunity by vaccines
• Short period (months): cholera vaccine
• Two years: TAB vaccine
• Three to five years: DPT vaccine
• Five or more years: BCG vaccine
• Ten years: Yellow fever vaccine
• Solid immunity: MMR (measles, mumps, and
rubella vaccines)
60. Levels of effectiveness
• Absolutely protective(100%): yellow fever vaccine
• Almost absolutely protective (99%): Variola, measles,
mumps, rubella vaccines, and diphtheria and tetanus
toxoids.
• Highly protective (80-95%): polio, BCG, Hepatitis B,
and pertussis vaccines.
• Moderately protective (40-60%) TAB, cholera vaccine,
and influenza killed vaccine.
61. The Cold Chain
• The "cold chain" is a system of storage and transport of
vaccines at low temperature from the manufacturer to the actual
vaccination site.
• The cold chain system is necessary because vaccine failure may
occur due to failure to store and transport under strict
temperature controls.
62. The Cold Chain Equipment
Cold chain equipment consists of the following:
(a) Walk in cold rooms: They are located at regional level,
meant to store vaccines up to 3 months and serve districts.
(b) Deep freezers (300 ltr) and Ice lined Refrigerators:
supplied to all districts and the WIC locations to store
vaccines. Deep freezers are used for making ice packs and to
store OPV and measles vaccines.
(c) Small deep freezers and ILR (140 ltr) : One set is
provided to PHCs, and Family Planning Centers
63. • (d) Cold boxes: Cold boxes are supplied to all
peripheral centers. These are used mainly for
transportation of the vaccines.
• (e) Vaccine carriers: Vaccine carriers are used to
carry small quantities of vaccines (16-20 vials) for the
out of reach sessions. 4 fully frozen ice packs are used
for lining the sides, and vials of DPT, DT, TT and
diluents should not be placed in direct contact with
frozen ice packs. The carriers should be closed tightly.
• (f) Ice packs: The ice packs contain water and no salt
should be added to it.
64. • Among the vaccines, Polio vaccine is the most sensitive to heat,
requiring storage at minus 20 degree C.
• Vaccines which must be stored in the FREEZER
COMPARTMENT are : polio and measles.
• Vaccines which must be stored in the COLD PART but never
allowed to freeze are : typhoid, DPT, tetanus toxoid, DT, BCG
and diluents
65. Vaccination Coverage
• Vaccination coverage is the percent of at risk or susceptible
individuals, or population who have been fully immunized
against particular diseases by vaccines or toxoids. To be
significantly effective in prevention of disease on mass or
community level at least a satisfactory proportion (75% or
more) of the at risk population must be immunized.
66. Herd immunity: At least 80-85% of the
population need to be vaccinated to reduce the
chance of somebody catching the disease –
even some one who has not been vaccinated-
to safe levels.
67. Ways of achieving satisfactory immunization
coverage
• Efficient immunization service; urban and rural
• Health awareness and cooperation of the public
• Periodic mass immunization campaigns, to cover those
who missed regular immunizations
• Outreach programs in rural and nomad areas, and home
visits
68. Application of active immunization
• Infants and children expanded immunization program
(schedule)
• Active immunization for adult females
• Vaccination for special occupations
• Vaccination for special life styles
• Vaccination for special environmental situations
• Vaccinations for special health status persons
• Vaccinations in travel
• Vaccines against bioterrorism
