Immunity Class- XII Biology

1. IMMUNITY
By- Dr R.K. Upadhyay

2. Ability of the host to fight the disease-causing
organisms/ antigen is Immunity
Acquired
immunity
-pathogen
specific
-After birth
Innate Immunity
● present at the
time of birth
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3. Innate Immunity
● It is non-specific type of defence
● That is present at the time of birth.
● Different types of barriers prevent the entry of the foreign agents
(antigens) into our body
(i) Physical barriers : Skin , Mucus coating of respiratory,
gastrointestinal and urogenital tracts
(ii) Physiological barriers : Acid in the stomach, saliva in the mouth,
tears from eyes–all prevent microbial growth.
(iii) Cellular barriers : leukocytes (WBC) of our body like
polymorpho-nuclear leukocytes (PMNL- monocytes and natural
killer , macrophages
(iv) Cytokine barriers : Interferons 3

4. Acquired Immunity
After birth
Pathogen specific
Characterized by memory
Primary response
-when our body encounters a pathogen for the
first time
-low intensity response
Secondary or anamnestic response
-Subsequent encounter with the same
pathogen elicits a highly intensified

5. “
● The primary and secondary immune responses are
carried out with the help of two special types of
lymphocytes present in our blood
1- B-lymphocytes
2- T-lymphocytes
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6. LYMPHOCYTE
Lymphocytes are one of several
different types of
white blood cells.
They all work together to fight
illness and disease.
About 25 % of the new
lymphocytes remain in the
bone marrow and become B
cells.
75 % travel to your thymus and
become T cells
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7. The B-lymphocytes produce proteins called antibodies.
The T-cells themselves do not secret antibodies but help B
cells t produce them.
The main functions of B cells are:
● to make antibodies against antigens,
● to perform the role of antigen-presenting
cells (APCs),
● to develop into memory B cells after
activation by antigen interaction.
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8. Y-shaped glycoprotein
Produced mainly by plasma
cells
Recognizing and binding to
particular antigens
Neutralize pathogens
Types-
IgG, IgM, IgA, IgD and IgE.
Structure of B cell - Immunoglobin
.
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9. STRUCTURE OF IG
4 Polypptides
H2 L 2
STRUCTURE
Heavy Chain (H)- 2
Light Chain (L) - 2
Disulphide bond
Constant region
Variable region
Antigen binding
site.
Red
Is the color of
blood, and because
of this it has
historically been
associated with
sacrifice, danger
and courage.
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10. Active and Passive Immunity
Active Immunity
● When a host is exposed to
antigens antibodies are
produced in the host body.
● Active immunity is slow and
takes time to give its full
effective response.
Exapmple
1- natural infection
2- vaccination
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PASSIVE IMMUNITY
When ready-made antibodies are directly
given to protec the body against foreign
agents, it is called passive immunity
Its action is fast
Examples-
1- Colostrums (Ig A) is passive immunity
2- Ready-made antibodies
3- Antitoxin
4- Antibodies against the snake venom

11. Vaccination and Immunisation
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based on the property of
‘memory’ of the immune system.
Vaccination is the administration of
a vaccine to help the immune system
develop protection from a disease.
Vaccines contain a microorganism or
virus in a weakened, live or killed state,
or proteins or toxins from the organism.
Immunization is the process whereby a
person is made immune or resistant to
an infectious disease, typically by the
administration of a vaccine.

12. Immune System in the Body
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Lymphoid organs
Tissue cells
Antibodies

13. Place your screenshot here
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Lymphoid organs:
● These are the organs where origin and/or
maturation and proliferation of lymphocytes occur.
● The primary lymphoid organs are bone marrow and
thymus where immature lymphocytes differentiate
into antigen-sensitive lymphocytes.
● After maturation the lymphocytes migrate to
secondary lymphoid organs like spleen, lymph
nodes, tonsils, Peyer’s patches of small intestine
and appendix.
● The secondary lymphoid organs provide the sites
for interaction of lymphocytes with the antigen,
which then proliferate to become effector cells

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The bone marrow is the main
lymphoid organ where all blood
cells including lymphocytes are
produced
is a lobed organ located near the
heart
● Both bone-marrow and thymus
provide micro-environments for
the development and maturation
of T-lymphocytes.

15. - The spleen is a large bean shaped organ.
-It mainly contains lymphocytes and
phagocytes.
-It acts as a filter of the blood by trapping
blood-borne microorganisms.
- Spleen also has a large reservoir of RBC.
Lymph nodes serve to trap the micro-organisms or
other antigens, which happen to get into the lymph
and tissue fluid.
Antigens trapped in the lymph nodes are
responsible for the activation of lymphocytes
present there and cause the immune response. 15

16. MALT
Within the lining of the
major tracts (respiratory,
digestive and urogenital
tracts
It constitutes about 50 %
of the lymphoid tissue in
human body.
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17. Allergies
● The exaggerated response of the immune system to
certain antigens present in the environment is called
allergy
● Allergens - substances to which such an immune
response
● The antibodies produced Ig E
● Symptoms - Sneezing, watery eyes, running nose and
difficulty in breathing.
● Histamine and Serotonin releases from the mast cells
● Antiallergen - anti-histamine, adrenalin and steroids 17

18. Auto Immunity
● An autoimmune disease is a condition
in which your immune system
mistakenly attacks your body.
Example-
Multiple sclerosis.
Myasthenia gravis.
Pernicious anemia.
Rheumatoid arthritis.
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19. THANK YOU
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