This document discusses different types of immunity. It describes innate or natural immunity which individuals are born with and includes species, racial, and individual immunity. Innate immunity acts as the first line of defense and is provided by the skin, mucous membranes, and phagocytic cells. Acquired or adaptive immunity develops after exposure to pathogens and includes both active and passive immunity. Acquired immunity has humoral components involving antibodies and cellular components involving T cells. Herd immunity is also discussed, where a community's immunity protects even unvaccinated individuals when a high percentage of the population is immune.

1. TYPES OF IMMUNITY
Nidhi Saxena
Department of
Microbiology

2. IMMUNITY
• Immunity is derived from Latin word “immunis” which means free
from burden. In this case burden refers to disease caused by
microorganisms or their toxic products.
• Immunity is defined as the state of resistance or in susceptibility to
disease caused by particular microorganisms or their toxic products.
• In biology, immunity is the balanced state of multicellular
organisms having adequate biological defenses to
fight infection, disease, or other unwanted biological invasion, while
having adequate tolerance to avoid allergy, and autoimmune
diseases.

3. FACTORS AFFECTS IMMUNITY
1. Host resistance
2. Dosage of organisms
3. Virulence of organisms

4. Types of
immunity
Natural or Innate
Immunity
Acquired or Adaptive or Specific
Immunity
Specie
s
immun
ity
Racial
immuni
ty
Individu
al
immunit
y
Active
Acquired
immunity
Passive
Acquired
immunity
Natural ArtificialNatural Artifici
al

5. NATURAL OR INNATE IMMUNITY
• Immunity with which an individual is born is called
innate or natural immunity.
• Innate immunity is inherited by the organism from the
parents and protects it from birth throughout life.
• 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.

6. TYPES OF INNATE IMMUNITY
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. For
example, 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. For example, Human are more
susceptible to skin infection whereas Cattles are more

7. 2. Racial immunity:
If one race is susceptible while other race is resistant
to same infection, then it is called Racial immunity.
For examples; certain African race are more resistant
to malaria and yellow fever but Asian or Americans are
susceptible to same infection.
Racial immunity is determined by difference in Socio-
economic status, habitat, culture feeding habits,
environments, genetic, etc.

8. 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.

9. MECHANISM OF INNATE IMMUNITY
1. Anatomical barrier
2. Physicochemical barrier
3. Phagocytic barrier or Phagocytosis
4. Inflammatory barrier or Inflammation

10. ANATOMICAL BARRIER
1. Skin:
Skin consists of two distinct layer; a thin outer layer
called epidermis and thick inner layer called dermis.
Epidermis consists of mostly dead cell filled with
keratin. Dermis is composed of connective tissue, hair
follicle, sebaceous gland and sweat gland.
Skin provides first line of defense by preventing entry
of microorganisms. However skin may be penetrated
by injury or insects.

12. 2. Mucous membrane:
• Mucus secreted by mucous membrane traps the
microorganisms and immobilises them.
• Microorganisms and dust particles can enter the
respiratory tract with air during breathing which are
trapped in the mucus.
• The cilia sweep the mucus loaded with
microorganisms and dust particles into the pharynx
(throat).
• From the pharynx it is thrown out or swallowed for
elimination with the faeces.

15. PHYSIOCHEMICAL BARRIER
1. Acid of the stomach kills most ingested
microorganisms
2. Bile does not allow growth of microorganisms
3. Cerumen (ear wax) traps dust particles, kills bacteria
and repels insects
4. Lysozyme is present in tissue fluids and in almost
all secretions e.g. sweat, urine, tears, saliva etc.
5. Nasal Hair. They filter out microbes and dust in
nose
6. Urine. It washes microbes from urethra

17. PHAGOCYTOSIS
• Phagocytosis is an important defense mechanism of
host to provide immunity. Most of the bacteria that
enter into host are killed by phagocytic cells such as
Neutrophils, monocytes and macrophages.
• Phagocytosis is an example of endocytosis.
• There are two types of endocytosis; phagocytosis and
pinocytosis.

19. INFLAMMATION
• Inflammation is an important defense mechanism of
host to prevent infection. It is induced in response to
tissue damage caused by microorganism, toxins or by
mechanical means.
• The inflammation may be acute; for eg. in response
to tissue damage or chronic; for eg. Arthritis, cancer
etc.
• Main aim of inflammation is to prevent spread of
injected microorganism or toxin from site of injection
and kill them on spot by phagocytosis.

20. CHARACTERISTICS OF
INFLAMMATION
1. Rubor: Redness
2. Tumor: Swelling
3. Calor: Heat
4. Dolor: Pain
5. Functio laesa: Loss of function

21. STEPS OF INFLAMMATORY
RESPONSE
1. Tissue damage caused by toxin, microorganism or
mechanical injury release histamine
2. Vasodilation: Histamine causes blood vessels
vasodilation.
3. Increased permeability: Histamine increases the
permeability of blood capillaries so that fluid
accumulates & causes edema.
4. Extravasation: Neutrophil migrates to the site of
tissue damage by the process of chemotaxis and
passes through capillaries wall and enter into tissue
space by the process called extravasation.

22. 5. Phagocytosis: Neutrophil kills the microorganism or
toxins by phagocytosis and release molecular
mediators that contributes to inflammatory
response. At the same time activates effectors cells.
6. Inflammatory response: As inflammatory response
develops, various cytokines and other inflammatory
mediators act on endothelium of local blood vessels,
including increased expression of cell adhesion
molecules (CAMs). The epithelium is then said to be
inflamed. Neutrophils are the first cell types to bind
to inflamed endothelium and extravasate into tissue.

24. ACQUIRED IMMUNITY
• Immunity which is developed later in life after
microbial infection in host is called as Acquired or
developed immunity. For example, 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.

25. TYPES OF ACQUIRED IMMUNITY
1. Active immunity:
• If host itself produces antibodies, it is called active
immunity.
a) Artificial active immunity: Immunity provided by
vaccination.
b) Natural active immunity: Immunity provided by natural
infection.
2. Passive immunity:
• If host does not produce antibodies itself but antibodies
produced in other host provides immunity, than it is known
as Passive immunity.

27. CHARACTERISTICS OF
ACQUIRED IMMUNITY
1. Specificity: It is the ability to differentiate between
antigens.
2. Diversity: It can recognise a vast variety of antigens.
3. Discrimination between Self and Non-self: It can
recognise and respond to foreign molecules (non-
self) and can avoid response to those molecules that
are present within the body (self) of the animal.
4. Memory: When the immune system encounters a
specific foreign agent, (e.g., a microbe) for the first
time, it generates immune response, eliminates the
invader and retains the memory for second

28. COMPONENTS OF ACQUIRED
IMMUNITY
Acquired immunity has two components:
1. Humeral immunity or Antibody mediated immune
system (AMIS)
2. Cellular immunity or cell mediated immune system
(CMIS)

29. HUMERAL IMMUNITY OR
ANTIBODY MEDIATED IMMUNE
SYSTEM (AMIS)
• The word ‘humor’ mean fluid.
• It consists of antibodies that circulate in the body fluids like
blood plasma and lymph.
• В lymphocytes (B cells) produce antibodies that regulate
humoral immunity.
• Humoral immunity or antibody-mediated immune system
(AMIS) provides defence against most extracellular bacterial
pathogens and viruses that infect through the respiratory and
intestinal tract.
Role of AMIS:
• The AMIS protects the body from viruses, some bacteria and

30. CELLULAR IMMUNITY OR CELL
MEDIATED IMMUNE SYSTEM
(CMIS)
• Lymphocytes are of two types: T lymphocytes and В
lymphocytes.
• Because T lymphocytes (T cells) mature in the thymus,
this immunity is also called T- cell immunity.
• The T-cells play two important functions—effector
and regulatory.
• The effector function includes cytolysis (destruction
of cells by immune processes) of cells infected with
microbes and tumour cells and lymphokine
production. The regulatory functions are either to

31. •Herd immunity also known as community immunity.
•Herd immunity occurs when a high percentage of the
community is immune to a disease (through vaccination
or other methods), making the spread of this disease
from person to person unlikely.
•Even individuals not vaccinated are offered some
protection because the disease has little opportunity to
spread within the community.
•Vaccines prevent many dangerous and deadly diseases.
•In India polio have been stamped out because of
HERD IMMUNITY

33. 1. Protection of those without immunity.
2. Evolutionary pressure.
3. Serotype replacement.
4. Eradication of diseases.
EFFECTS OF HERD IMMUNITY

34. •Individuals who are immune to a disease act as a
barrier in the spread of disease.
•There are certain groups of people who cannot get
vaccinated and are vulnerable to disease:- babies,
pregnant women and immunocompromised people,
such as those receiving chemotherapy or organ
transplants.
•If enough people are vaccinated against dangerous
diseases, those who are susceptible and cannot get
vaccinated are protected because the germ will not be
able to “find” those susceptible individuals.
MECHANISM OF HERD IMMUNITY

35. 1) Innate herd immunity:
 It is genetically determined physiological changes
with respect to antibody production or other
defence mechanism in a herd.
 It does not depend on the previous exposure of herd
with infection or it may arise in a herd through
prolonged exposure to an infection or natural
selection.
2) Acquired herd immunity:
 It is a type of herd immunity where a sufficient
number of its members have actually been exposed
naturally or artificially to infectious agents during
TYPES OF HERD IMMUNITY

36. REFERENCES
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7. Google
4-Feb-21 NIDHI SAXENA, DEPARTMENT OF MICROBIOLOGY 36