Chapter8: Human Health and Diseases; Class XII; BIOLOGY; NEET; CBSE

1. IMMUNOLOGY
SHUBHADEEP BHATTACHARJEE

2. • IMMUNITY: IT IS THE ABILITY OF AN ORGANISM TO RESIST OR DEFEND ITSELF
FROM A DISEASE
• IMMUNE SYSTEM: BODY’S DEFENSE SYSTEM TO FIGHT AGAINST DISEASES AND
INFECTIONS.
COMPRISES OF ORGANS (SPLEEN, THYMUS) AND CELLS
(LEUKOCYTES, NK CELLS, MACROPHAGES)
TYPES OF IMMUNITY
IMMUNITY
Innate
immunity
Acquired
ImmunityActive immunity
Passive
Immunity

3. INNATE IMMUNITY
• IT IS PRESENT FROM THE BIRTH
• IT IS NON-SPECIFIC
• CONSISTS OF LAYERS OF BARRIERS
PHYSICAL BARRIERS: Epidermis, Mucous membranes (GI
tract/ Respiratory tract/ Urogenital tract)
PHYSIOLOGICAL BARRIERS: Sweat, tears, acid in the
stomach, saliva
CELLULAR BARRIERS: WBCs (Polymorphonuclear
leucocytes, Monocytes, Natural killer lymphocytes and
Macrophages)

4. CYTOKINE BARRIERS: Interferons produced by virus
infected cells protect non-infected cells from further
viral infections

5. ACQUIRED IMMUNITY:
• NOT PRESENT FROM BIRTH
• ACQUIRED EITHER BY CONTRACTING A DISEASE OR BY VACCINATION
• PATHOGEN SPECIFIC
PRIMARY RESPONSE: when immune system encounters a
disease for the first time.
Generates memory of the encounter and produces
antibody that helps to resist subsequent infections.

6. • ACQUIRED IMMUNITY
Secondary Response: Happens when a previously encountered pathogen
enters a host
Defense based on the memory and Ab generated during
the 1’response.
It’s much more heightened as compared to the
1’response.
HUMORAL IMMUNITY
CELL MEDIATED IMMUNITY

7. • HUMORAL IMMUNITY:
ACHIEVED WITH THE HELP OF B-LYMPHOCYTES
B-LYMPHOCYTES PRODUCE SPECIALIZED PROTEINS CALLED AS ANTIBODIES.
THESE ANTIBODIES ARE FOUND IN THE BLOOD AND THE LYMPH AND HENCE
IS CALLED AS ANTIBODY MEDIATED OR HUMORAL IMMUNITY.
• CELL MEDIATED IMMUNITY:
ACHIEVED WITH THE HELP OF T-LYMPHOCYTES
CELLULAR IN NATURE AND HENCE CALLED AS CELL MEDIATED IMMUNITY
T-CELLS DO NOT PRODUCE ANTIBODIES BUT HELP B-CELLS TO PRODUCE IT.
T-CELLS ARE OF THREE TYPES: KILLER/ HELPER/ SUPPRESSOR

8. ANTIBODIES:
• PROTEIN MOLECULES CALLED
IMMUNOGLOBULINS (Ig)
• VARIOUS TYPES: IgM, IgA, IgG, IgE
• CONSISTS OF FOUR POLYPEPTIDE CHAINS:
• TWO ARE LONG AND ARE CALLED HEAVY
CHAINS (H- CHAIN)
TWO ARE SHORT AND ARE CALLED LIGHT
CHAINS (L-CHAINS)
ANTIBODIES ARE HENCE REPRESENTED AS
H2L2

9. ACTIVE & PASSIVE IMMUNITY
Active Immunity Passive Immunity
Develops due to contact with a pathogen or
it’s antigen.
It is developed when readymade antibodies
are injected into the body.
No side effects or only a few. It may trigger reactions.
It is long lasting. It is short lived and lasts for only a few days.
It takes time to develop. It is specifically used when the immune
response has to be faster.

10. VACCINATION & IMMUNISATION
• VACCINATION: IT IS THE PROCESS OF INTRODUCTION OF VACCINES (WEAKENED OR
INACTIVE PATHOGENS) INTO A PERSON TO PROVIDE PROTECTION AGAINST A
DISEASE
• IMMUNISATION: IT IS THE PROCESS BY WHICH THE BODY PRODUCE ANTIBODY
AGAINST THE VACCINE PREVENTABLE DISEASE THROUGH ADMINISTRATION OF
SPECIFIC DOSAGE
• VACCINATION PROVIDES IMMUNIZATION AFTER A TIME GAP
EXAMPLES OF VACCINES: TETANUS VACCINES, HEPATITIS-B VACCINE

11. ALLERGIES
• EXAGGERATED OR HYPERSENSITIVE REACTION OF THE IMMUNE SYSTEM TO
CERTAIN ANTIGENS PRESENT IN THE ENVIRONMENT IS CALLED ALLERGY
• SUBSTANCES OR AGENTS WHICH PRODUCE AN IMMUNE RESPONSE IN AN
INDIVIDUAL IS CALLED AS ALLERGENS, E.G., POLLEN GRAINS, ANIMAL DANDER,
DUST, DRUGS LIKE PENICILLIN ETC.
• IgE ANTIBODIES ARE PRODUCED IN RESPONSE TO ALLERGENS.
• SYMPTOMS:
 I. SNEEZING, II. WATERY EYES, III. RUNNING NOSE, IV. DIFFICULTY IN
BREATHING
CHEMICALS LIKE HISTAMINE AND SEROTONIN RELEASED FROM MAST CELLS
CAUSES ALLERGY
DRUGS: ANTI-HISTAMINE, ADRENALINE AND STEROIDS

12. • Can a new born child show
allergic reactions?
• During skin grafts or organ
donation surgeries, there is a
possibility of the donated
organ to get rejected by the
recipient. Think about the
mechanism behind this.
• Donations are only advised
between close relatives. Why?

13. AUTO-IMMUNITY
• ABNORMALITY OF THE IMMUNE SYSTEM
• IMMUNE SYSTEM STARTS REJECTING ITS OWN BODY CELLS OR SELF CELLS
• EG: RHEUMATOID ARTHRITIS, ADDISONS DISEASE, HOSHIMOTO DISEASE.

14. ORGANS OF THE IMMUNE SYSTEM
• PRIMARY LYMPHOID ORGANS: THOSE ORGANS WHERE ORIGIN AND
MATURATION AND PROLIFERATION OF LYMPHOCYTES OCCUR.
A. BONE MARROW:
• MAIN LYMPHOID ORGAN WHERE ALL BLOOD CELLS INCLUDING LYMPHOCYTES
ARE FORMED.
• SITE OF MATURATION AND PROLIFERATION OF THE B-LYMPHOCYTES.
B. THYMUS:
• LOBED ORGAN LOCATED NEAR THE HEART AND BENEATH THE BREASTPLATE
• REDUCES IN SIZE WITH AGE
• SITE OF MATURATION AND DEVELOPMENT OF T- LYMPHOCYTES

15. PRIMARY LYMPHOID
ORGANS

16. • SECONDARY LYMPHOID ORGANS: THOSE ORGANS WHERE
LYMPHOCYTES INTERACT WITH THE ANTIGENS AND
PROLIFERATE TO BECOME EFFECTOR CELLS
a. SPLEEN:
• LARGE BEAN-SHAPED ORGAN CONTAINING LYMPHOCYTES
AND PHAGOCYTIC CELLS
• NATURAL BLOOD-FILTER- TRAPS BLOOD-BORNE
PATHOGENS
• GRAVEYARD OF RBCS
B. LYMPH NODES:
• SMALL SOLID STRUCTURE PRESENT AT DIFFERENT POINTS
ALONG THE LYMPHATIC SYSTEM
• TRAPS THE MICROORGANISMS AND OTHER ANTIGENS THAT
ENTER THE LYMPH
• AG TRAPPED IN THE LYMPH NODES ARE RESPONSIBLE FOR
THE ACTIVATION OF LYMPHOCYTES AND PRODUCTION OF
IMMUNE RESPONSE

17. C. MUCOSAL
ASSOCIATED
LYMPHOID TISSUE
(MALT):
• MASSES OF
LYMPHOID TISSUE
PRESENT IN THE
MUCOSA OF
RESPIRATORY,
DIGESTIVE AND
UROGENITAL
TRACTS.
• 50% OF THE
LYMPHOID TISSUE IN

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