Immunity is the ability of the body to defend itself against disease-causing organisms. It is the resistance or insusceptibility showed against the foreign particles or disease causing agents.

1. Anup Muni Bajracharya
&
ITS TYPES

2. Immunology
• the study of the human immune
system.
• word "immunity" derives from
the Latin immunis, meaning exemption
from military service, tax payments or
other public services.
• Here it means free from burden. In this
case burden refers to disease caused
by microorganisms or their toxic
products.
• Study of cells, organs and chemical
components of the immune system
which fight against the infectious
agents.

3. Immunity
• Ability of body to specifically counteract with foreign
organisms.
• State of resistance or insusceptibility exhibited by the host to
toxic chemicals,mos and foreign cells.

4. History of Immunology

5. Thucydides
➢ The earliest known mention of immunity
was during the plague of Athens in 430 BC
by Thucydides.
➢ He was dubbed the father of "scientific
history" due to his strict standards of
evidence-gathering and analysis in terms of
cause and effect without reference to
intervention by the gods.
➢ He noted that people who had recovered
from a previous bout of the disease could
nurse the sick without contracting the
illness a second time.

6. Chinese-smallpox
➢ The Chinese practiced the oldest documented use of
variolation, dating back to the fifteenth century.
➢ They implemented a method of "nasal insufflation"
administered by blowing powdered smallpox material, usually
scabs or pus , up the nostrils.

8. Edward Jenner
scientist who pioneered the concept of
vaccines including creating the smallpox
vaccine, the world's first vaccine.
Born 17 May 1749
Berkeley,
Gloucestershire, England
Died 26 January
1823 (aged 73)
Berkeley,
Gloucestershire, England
Nationality British
Known for Smallpox vaccine
Vaccination
Scientific career
Fields Medicine/surgery,
natural history
Academic advisors John Hunter

9. In 1796, he carried out his now famous
experiment on eight-year-old James Phipps.
Jenner inserted pus taken from a cowpox
pustule and inserted it into an incision on the
boy's arm.
He was testing his theory that milkmaids who
suffered the mild disease of cowpox never
contracted smallpox, one of the greatest killers
of the period, particularly among children.
Jenner subsequently proved that having been
inoculated with cowpox Phipps was immune to
smallpox.
He submitted a paper to the Royal Society in
1797 describing his experiment, but was told
that his ideas were too revolutionary and that
he needed more proof.
Undaunted, Jenner experimented on several
other children, including his own 11-month-old
son.
In 1798, the results were finally published and
Jenner coined the word vaccine from the Latin
'vacca' for cow.
Dr Jenner performing his first
vaccination on James Phipps, a boy
of age 8. 14 May 1796

10. Louis Pasteur- Chicken cholera
• In the summer of 1880, Pasteur found a
vaccine by chance, after forgetting one
of his cultures.
• With the help of a colleague Charles
Chamberland, he showed that Chicken
cholera germs from an old culture that
had been around for some time lost
their ability to transmit the disease.
• The inoculated chickens did not die.
• Pasteur repeated what he had done but
with a fresh culture of chicken cholera
germs.
• Pasteur reasoned that a new culture
would provide more potent germs.

11. • Two groups of chickens were
inoculated; one that had been
given the old culture and one
group that had not.
• Those chickens that had been
given the old culture survived,
those that had not died.
• The chickens that had been
inoculated with the old culture
had become immune to chicken
cholera.
• Pasteur believed that their bodies
had used the weaker strain of
germ to form a defence against
the more powerful germs in the
fresher culture.
• Pasteur had found a way of
producing the resistance without
the risk of the disease.

12. Innate or natural immunity
Acquired immunity

13. Innate or Natural immunity
• Immunity with which an individual is born is
called innate or natural immunity.
• Innate immunity is provided by various
components such as Skin, Mucus membrane,
Phagocytic cells etc.
• Innate immunity acts as first line of defense to
particular microorganisms.

14. Mechanism of innate immunity
• Anatomical barrier
• Physicochemical barrier
• Phagocytic barrier or Phagocytosis
• Inflammatory barrier or Inflammation

16. Types of innate immunity
• Species immunity
• Racial immunity
• Individual immunity

17. 1. Species immunity
• If one species is resistant to certain infection and the other
species is susceptible to the same infection then it is called
as species immunity.
• Anatomic, physiological and metabolic differences between
species determine species immunity.
• Eg- Birds are resistant to anthrax but Human are
susceptible. It is simply because higher body temperature
of birds kills Bacillus anthracis.
• Anatomic differences between species also determine
species immunity. Eg- Human are more susceptible to skin
infection whereas Cattles are more resistant to the same
skin infection. It is because of tough and hairy skin (hides)
of Cattles.
• Entire human species is resistance to the plant pathogens.

18. 2. Racial immunity
• If one race is susceptible while other race is resistant to
same infection, then it is called Racial immunity.
• Eg-certain African race are more resistant to malaria and
yellow fever where are Asian or Americans are susceptible
to same infection.
• Similarly Orientals (East Asia) are relatively resistant to
syphilis.
• Algerian sheep, for example, are immune to anthrax, a
disease commonly fatal to other breeds of sheep
• Racial immunity is determined by difference in Socio-
economic status, habitat, culture feeding habits,
environments, genetic, etc.

20. 3. Individual immunity
• If one individual of certain race or cast is resistant while other
individuals of same race or cast are susceptible to certain infection,
then it is called as individual immunity
• Individual immunity is determined by various factors such as health
status, nutritional status, previous illness, personal hygiene, genetic
differences etc.
• For examples; Individual with genetic deficiency of glucose-6
phosphate dehydrogenase are resistant to Malaria.

23. Acquired or Developed immunity:
• Immunity which is developed later in life after microbial infection in
host is called as Acquired or developed immunity.
• If an individual is infected with chicken pox virus, he/she become
resistant to same virus in later life.
• Acquired immunity is provided by
– Antibodies and certain T-lymphocytes.
• Components of acquired immunity such as Antibodies and T- cells
are specific to particular microorganism.
Therefore acquired immunity is also known as Specific
immunity.
Characteristics of Acquired immunity
• Specificity
• Self/non-self recognition
• Immunological memory
• Diversity

24. • Types of acquired immunity:
• Active immunity
• Passive immunity

25. 1. Active immunity:
• The immunity induced by exposure to a
foreign antigen is called active immunity.
• the resistance developed by an individual
after contact with foreign antigens, e.g.,
microorganisms. This contact may be in
the form of:
• clinical or subclinical infection,
• immunization with live or killed
infectious agents or their antigens,
or
• exposure to microbial products, such as
toxins and toxoids.
• If host itself produces antibodies, it is
called active immunity.
• It is of two types
• Naturally acquired active immunity:
• immunity provided by natural infection.
• Artificially acquired active immunity:
• Immunity provided by vaccination.
Vaccination

26. 2. Passive immunity:
• When immunity is conferred by
transfer of serum or lymphocytes
from a specifically immunized
individual, it is known as passive
immunity.
• If host does not produce antibodies
itself but antibodies produced in
other host provides immunity, than
it is known as Passive immunity.
It is of two types
– Naturally acquired passive
immunity: IgG antibody produced
in mother cross placenta and
protects fetus.
– Artificially acquired passive
immunity: if preformed antibody
are injected into host for immunity.
Eg. Anti-venom, Rabies vaccine (*it
is not a vaccine, it is preformed
anti-rabies antibody)

27. Passive Immunity
Convalescent plasma therapy

28. Difference between Active and Passive Immunity

30. What is herd immunity?
• When most of a population is immune to an infectious disease, this provides
indirect protection—or population immunity (also called herd immunity or herd
protection)—to those who are not immune to the disease.
• For example, if 80% of a population is immune to a virus, four out of every five
people who encounter someone with the disease won’t get sick (and won’t
spread the disease any further).

31. • Vaccination programs create herd immunity by
greatly reducing the number of susceptible
individuals in a population.
• Even if some individuals in the population are not
vaccinated, as long as a certain percentage is
immune (either naturally or artificially), the few
susceptible individuals are unlikely to be exposed
to the pathogen.
• However, because new individuals are constantly
entering populations (for example, through birth
or relocation), vaccination programs are
necessary to maintain herd immunity.