Acquired immunity

1. Acquired Immunity

2. The immune system
Immune system
• Anatomic barriers (Skin, mucous
membranes)
• Physological barriers
(temperature, pH)
• Phagocytic Barriers (cells that eat
invaders)
• Inflammatory barriers (redness,
swelling, heat and pain)
• Antigen specificity
• Diversity
• Immunological memory
• Self/nonself recognition
Innate (non-specific) immunityAdaptive (specific) immunity

3. Humoral and cellular immunity
(antibody mediated or cellular)

4. B cells
B-cell
Antigen
Antibody secreting B cell
Soluble antibodies, circculate in the body
Surface bound antibody

5. B-cell
Plasma cell
Virus killed

6. T cells
Two types:
Helper T cells (Th): activates other cells
Cytotoxic T cells (Tc): can kill other cells
T cells can only recognize antigens
associated with certain molecules (MHC)

7. Presentation of antigens
to T cells
Proteins (peptides) from inside the cell are
presented by MHC I molecules to Tc cells.
Proteins (peptides) from the outside of
cells are presented by MHC II molecules to
Th cells.
MHC I on almost all cells
MHC II on specialized antigen-presenting
cells

8. ACQUIRED IMMUNITY
The resistance that an individual acquires during life
Two types :
1. Active Immunity
2. Passive Immunity
Active Immunity : Resistance developed as a result of
antigenic stimulus
Passive Immunity : Resistance transmitted passively in
ready made form

9. Active Immunity
- Adaptive immunity : Adaptive response of host
to specific pathogen or antigen
- Active functioning of the host’s immune
apparatus, synthesis antibodies and
immunologically active cells
- Latent period
- Negative phase
- Long lasting
- Secondary response is faster
- Immunological memory
- More effective and gives better protection

10. Passive Immunity
Ready made form of immunity
Recipients immune system plays no active role
No antigenic stimulus
No latent period, protection effective immediately
No negative phase
Transient , lasting for few weeks to days
No secondary response, diminishes with repetition
Less effective and Inferior o active immunity
Acts immediately and ‘Instant form of Immunity’

11. Active Immunity
Natural Active Immunity :
- Results from a clinical or inapparent infection by microbe
- Measles and Poliomyelitis
- Life long following many viral infection
- Immunity following bacterial infection is less permanent than
viral infections
- Premunition : Immunity to re infection lasts till the original
infection remain active. Eg: Syphilis
- In Chancroid : no effective immunity against re infection
even during active infection
Natural Active Immunity
Artificial Active immunity

12. Artificial Active Immunity
- Resistance induced by Vaccines – live or
killed microorganisms or their products
- Live vaccines : Parallels natural infection
- Gives protection for a long period
- requires booster doses
- Killed vaccines : Less immunogenic
- Protection lasts for a short period
- Repeated doses required
- Parenteral administration required to initiate
humoral antibody response

13. Passive Immunity
Natural passive immunity :
- Mother to baby : Maternal antibodies, Colostrum
- Immunological independence at 3-6 months
- Active immunization of mothers during pregnancy
improves the passive immunity in infants
- Tetanus toxoid in tetanus prone communities
Natural Passive Immunity
Artificial Passive Immunity

14. Artificial Passive Immunity :
Administration of antibodies
- Hyper immune sera
- Hyper immune globulin
- Convalescent sera
- Pooled Human gamma globulin
Treatment of infections in non immune persons
Confers immediate and Temporary protection
Suppression of active immunity in
Erythroblastosis fetalis

15. Passive ImmunityPassive Immunity
·Antibodies are obtained from someone
else
·Conferred naturally from a mother to her
foetus
·Conferred artificially from immune serum or
gamma globulin
·Immunological memory does not occur
·Protection provided by “borrowed
antibodies” is temporary.

16. Active and Passive Active and Passive
Immunity/VaccinesImmunity/Vaccines
Slide
12.34
·B cells
encounter
antigens and
produce
antibodies
·Active immunity
can be naturally
or artificially
acquired

17. Combined Immunization :
Active & Passive
Adoptive immunity : Injection of
immunologically competent lymphocytes
(Transfer factor)
Measurement of immunity
- Antibody titers by
- Agglutination & Precipitation
- CFT, HI
- NT & ELISA
Local Immunity
Herd Immunity