There are three main types of immunity: innate, acquired, and herd immunity. Innate immunity is resistance possessed from birth and provides the initial defense. Acquired immunity develops during one's lifetime through exposure to antigens and allows the body to recognize and eliminate specific foreign substances with antigen specificity and immunological memory. Acquired immunity can be active, developed from natural exposure or artificial vaccination, or passive, developed from transfer of antibodies rather than active immune response. Herd immunity occurs when a sufficient percentage of a population is immune, either through prior infection or vaccination, reducing infections within the overall community.

1. Immunity
-Gaveesh Dixit

2. • It is the resistance exhibited by the host against any
foreign antigen and towards the injury caused by any
microorganisms and their products.
• Types:
1.Innate ; 2.Acquired ; 3.Herd Immunity
Definition and types:

3. Innate immunity
It is the resistance possessed by an individual by birth
i.e. Inherited
It provides first line of defence to our body.
There are 3 levels of innate immunity:
1.Species level
2.Racial level
3. Individual level

4. Acquired immunity
• It is the resistance acquired by an individual during
the lifetime by recognising and selectively eliminating
the specific foreign molecules.

5. Characteristics :
• Antigen specificity: This immunity can distinguish
between different foreign organisms.
• Diversity: Immune system is capable of producing
different type of molecules.
• Immunologic memory: Immune system is capable of
forming memory of next encounter.

6. Active immunity:
• Also known as adaptive immunity.
• Resistance developed by an individual as a result of
antigenic stimulus.
• It is used for prophylaxis to increase the body
resistance.
• It is of two types: Natural active and Artificial active.

7. Passive immunity
• Resistance transmitted passively to a recipient in a recipient
form
• It is used for treatment of acute infection.
• There are two types :
1. Natural passive immunity
2. Artificial passive immunity

8. Types of acquired immunity

9. Herd immunity:
• Overall level of immunity in a community.
• It occurs when a sufficient percentage of a
population has become immune to an infection,
whether through previous infections or vaccination.
• Once the herd immunity has been reached, disease
gradually disappears from a population and may
result in eradication or permanent reduction of
infections to zero if achieved worldwide.

10. Thank you