Adaptive immunity develops in response to stimuli that induce antibody production. It has two main branches: active immunity and passive immunity. Active immunity involves the immune system developing its own response through infection or vaccination, resulting in immunological memory. Passive immunity involves receiving ready-made antibodies from another source, providing immediate but temporary protection without memory. Adaptive immunity is classified as actively or passively acquired, with actively acquired immunity developing through natural exposure or vaccination, while passively acquired immunity results from maternal antibody transfer or immunoglobulin administration.

1. Adaptive immunity

2. Lecture Outline
• Introduction of Adaptive immunity
• Classification and Characteristics

3. Definition
• Adaptive immunity: also called as acquired immune response
• Usually the resistance that an individual acquires during life to
various infections
• Develops in response to a natural or artificial stimuli which
able to induce antibody production
• 2 main branches: Active and Passive

4. Acquired
immunity
Active
Infection (Sub
clinical)
Antibody
production
Vaccination
Passive
Transplacental or
via colostrum
(IgG or IgA)
Administration of
immunoglobulins
(by injection)

5. Characteristics
• Composed of highly specialized, systemic cells and processes that
eliminate or prevent pathogenic growth
• The major functions of the adaptive immune system include:
1. The recognition of specific “non-self” antigens in the presence of “self”,
during the process of antigen presentation
2. The generation of responses that are tailored to maximally eliminate
specific pathogens or pathogen infected cells
3. The development of immunological memory, in which each pathogen is
“remembered” by a signature antibody
• These memory cells can be called upon to quickly eliminate a pathogen
should subsequent infections occur

6. Classification
Acquired Immunity
(Specific immunity)
Actively acquired
immunity
Naturally actively
acquired immunity
Artificially actively
acquired immunity
Passively acquired
immunity
Naturally passively
acquired immunity
Artificially passively
acquired immunity

7. Actively acquiredimmunity
• When B and T cells are activated by a pathogen, memory B-cells and T-
cells develop
• memory cells will “remember” each specific pathogen encountered &
are able to mount a strong response if the pathogen is detected again
• This type of immunity is both active & adaptive because the body's
immune system prepares itself for future challenges
• Active immunity often involves both the cell-mediated and humoral
aspects of immunity
• There may be a negative phase during the development of active
immunity due to combination of the antigen with the produced
antibody

10. Passively acquired immunity
• Immunity gain in the form of readymade antibodies, from one individual to
another
• Passive immunization is used when there is a high risk of infection & insufficient
time for the body to develop its own immune response
• To reduce the symptoms of ongoing or immunosuppressive diseases
• Passive immunity provides immediate protection, but the body does not develop
memory, therefore the patient is at risk of being infected by the same pathogen
later
• No lag phase as antibodies are readily administered to the body
• applicable in immundeficient patients as they are unable to produce antibodies

11. Actively acquired immunity Passively acquired immunity
Produced by active functioning of the
immune system
Received passively. No involvement of
immune system
Stimulated by infections, antigens
(vaccines, allergens)
Acquired by administration of Abs or
sensitized T cells
Provides effective and long lasting
immunity
Immunity is less effective and transient
There is a lag phase (latent period) required
for the formation of Abs
Offers immediate protection
Immunological memory is present.
Subsequent contact with Ag will have a
booster effect
No memory. Subsequent administration of
Abs is less effective due to immune
elimination
Negative phase may occur due to the
combination of Ag with preexisting Ab
No negative phase
Not applicable in immunodeficient hosts Applicable in immunodeficient hosts
Active immunization is mainly employed for
prophylaxis
Passive immunization has therapeutic and
prophylactic uses

12. Naturally acquired active immunity
• immunity occurs when a person is exposed to a live pathogen, and develops a
primary immune response, which leads to immunological memory
• This type of immunity is “natural” because it is not induced by deliberate
exposure
 Eg: people exposed to polio virus
repeatedly during childhood will
develop natural active immunity
 people who recover from viral
diseases (smallpox, chicken pox,
measles) will develop life long natural
active immunity

13. Naturally acquired passive immunity
• Antibody-mediated immunity
conveyed to a fetus by its mother
(maternal IgG antibodies) during
pregnancy
• Passive immunity is also provided
through the transfer of IgA
antibodies found in breast milk
that are transferred to the gut of
the infant, protecting against
bacterial infections

14. Artificially acquiredactive immunity
• Artificially acquired active immunity can be induced by a
vaccine, a substance that contains antigen
• A vaccine stimulates a primary response against the antigen
without causing symptoms of the disease
• The vaccine usually consists of,
• a) dead or live attenuated microorganisms
• b) altered microorganism
• c) part of the microorganism
• d) a product of the microorganism

15. Artificially acquiredpassive immunity
• is a short-term immunization induced by the transfer of
antibodies, which can be administered in several forms;
• as human or animal blood plasma, as pooled human
immunoglobulin for intravenous (IVIG), intramuscular (IG) use
& in the form of monoclonal antibodies (MAb)
• there is also a potential risk for hypersensitivity reactions &
serum sickness, especially from gamma globulin of non-
human origin
• Eg: Tetanus antitoxin (Antitetanus serum), Diphtheria antitoxin

17. Comparison

18. Lecture Summary
• Definition of Adaptive immunity
• classification
• examples for adaptive immune responses

19. References
• Coico R, Sunshine G (2015) Immunology: A Short Course. John
Wiley & Sons Ltd.

20. Let’s Talk…….
1. What are the three types of innate immunity? Explain each.
2. What are the mechanisms of innate immunity? Explain
each.
3. What are the types of adaptive immunity? Explain each
with examples.
4. Compare and contrast innate and adaptive immunity.

21. Recommended reading/Guide for Self-
regulated learning
• Mohanty SK, Leela KS (2014) Text Book of Immunology
Course. Jaypee Brothers Medical Publishers (P) Ltd.

22. THANK YOU