Acquired immunity

Immunity we acquire as a result of Infection/ Vaccinaion

1. Dr.Riyaz Sheriff M.D ….

2. IMMUNITY
IMMUNITY
INNATE
NON
SPECIFIC
SPECIES
RACE
INDIVIDUAL
SPECIFIC
SPECIES
RACE
INDIVIDUAL
ACQUIRED
ACTIVE
NATURAL
ARTIFICIAL
PASSIVE
NATURAL
ARTIFICIAL

3. ACQUIRED IMMUNITY
•Immunity which a person acquired during his
lifetime
•Not related to innate immunity

4. Acquired IMMUNITY
ACQUIRED
ACTIVE
NATURAL ARTIFICIAL
PASSIVE
NATURAL ARTIFICIAL

5. Acquired active
IMMUNITY
ACQUIRED
ACTIVE
NATURAL ARTIFICIAL
Resistance developed as a result of
antigenic stimulus
Also called “Adaptive Immunity”
Active involvement of host immune
apparatus
Leads to production of antibodies /
Immunologically active cells
Takes time to set in after infection

6. Acquired active
IMMUNITY
ACQUIRED
ACTIVE
NATURAL ARTIFICIAL
Initial NEGATIVE PHASE : The
level of measureable immunity is
lower than it was before exposure to
antigen.
The antigen combines with the
existing antibody leading to reduction
in existing levels of antibody.

7. Acquired active IMMUNITY
ACQUIRED
ACTIVE
NATURAL ARTIFICIAL
Once active immunity sets in
It is long lasting
One second exposure to same antigen the
immune response is quick and abundant
:SECONDARY RESPONSE
Development of humoral & cellular
immunity
Immunological memory
Active immunization is more effective and
confers better protection
May be Natural or Artificial

8. Natural active IMMUNITY
May be as a result of clinical or inapparent infection
Measles infection gives the patient life long immunity
Adults in developing countries have natural active immunity against
polio because of inapparent infections in childhood
Duration of immunity depends on the pathogen
Short term –Eg. Influenza
Long term -Eg. Measeles, chicken pox
Why common cold does not provide us immunity ???
Antigenic
variation

9. natural active IMMUNITY
Bacterial infections provide with less degree of
immunity
PREMUNITION –Seen in syphilis . The immunity to
reinfectionslasts only till the original infection is
active.
Chancroiddoes not provide the person with any
immunity . Person may develop lesions following
reinfectioneven when original infection is active.

10. Artificial active immunity
•Resistance induced by vaccines
•Vaccines are preparations of live or killed
microorganisms or their products used for
immunization
•Bacterial vaccines
–Live : BCG vaccine
–Killed: Cholera vaccine
–Subunit : Typhoid Vi antigen
–Bacterial products: Tetanus toxoid
•Viral vaccines
–Live : OPV-Sabin
–Killed : IPV –Salk
–Subunit : Hepatitis B Vaccine

11. Vaccines
LIVE VACCINES
•Infection without disease
•Immunity lasts for several
years
•Booster doses MAY BE
needed
•Can be given orally or
parenterally
KILLED VACCINES
•No infective stage
•Less immunogenic
•Repeated doses needed
–Primary dose
–Booster dose
•Oral doses not effective
•Parenteraldoses given with
adjuvant to increase
humoral immunity

12. Passive immunity
oNo infection
oReadymade antibodies are
administered
oNo latent period
oNo negative phase
oImmediate protection
oImmunity lasts for short
duration till antibodies are
metabolized
oNo secondary response
oPassive immunity decreases
with repetition

13. Types of passive acquired
immunity
PASSIVE
NATURAL ARTIFICIAL
Resistance transferred from mother to baby
Via placenta
Breast milk –colostrum–IgA
IgMproduction by fetus can start from 20
th
week of intrauterine life
Inadequate immunity at birth
By 3 months of age –immunological independence
•<3 months –Pediatric infections are common
Active immunization of mother provides passive immunity to infants
Eg. Tetanus toxoidduring pregnancy

14. Types of passive acquired
immunity
PASSIVE
NATURAL ARTIFICIALResistance transferred by
administration of antibodies
Hyper immune sera
Convalescent sera
Pooled human Ɣ globulin
Used for prophylaxis and therapy

15. Hyperimmunesera
•Anti-tetanus serum (ATS)
•Prepared from hyperimmunizedhorses
•Temporary protection
•Disadvantages
•Hypersensitivity
•Immune elimination
•In use
–Hyperimmuneglobulin of human origin
Animal origin in use
Anti-Gas gangrene sera
Anti-Botulinumsera
Antivenoms

16. Convalescent sera
•Sera of patients recovering from disease
•Contain high levels of antibody specific to the disease
•Use –Viral infections like Hepatitis A
Pooled human Ɣ globulin
•Ɣ globulin from pooled sera of healthy adults
•Has antibodies to all pathogens prevalent in the area
•Use –Rxof patients with immunodeficiencies

17. Indications for passive
immunization
•Immediate and temporary protection of a
person at risk of developing infection
•To arrest overactive active immunity
Eg. Rh incompatibility

18. Combined immunization
•Combination of active and passive methods
•Passive immunization for immediate
protection
•Tetanus
•TIG in one arm + TT in other arm
•Followed by complete schedule of tetanus
vaccination

19. Adoptive immunity
•Special type of immunization
•Injection of immunologically competent
lymphocytes TRANSFER FACTOR
•Tried in treatment of LepromatousLeprosy

20. Local immunity
•Besredka
•Treatment of infections in a localized area
•Polio –
–Systemic immunity by IPV
•Does not prevent multiplication of virus in the gut
–This is achieved by OPV
•Influenza
–Killed vaccine brings about a humoral response
•Not enough to prevent infection
•Intra nasal live virus injection/ natural infection provides
local immunity
–IgA

21. Immunoglobulin A (IgA)
•Secretory IgA
•Produced locally by plasma cells on mucosal
surfaces / Secretory glands
•With exposure to an antigen
Specific IgA is produced
•Mucosal defense
•Handling of antigens contracted from food and
external environment

22. Herd immunity
Overall immunity in a community
Useful in control of epidemics
•When LARGE NUMBER of people in a community are
immune to a specific pathogen Herd immunity is
SATISFACTORY
•Eradication of communicable disease lies in development of
good herd immunity rather than developing individual
immunity

23. Measurement of immunity
•Practically not possible to measure accurately
•Simple method is to demonstrate the presence of a
specific antibody
–Not reliable as one pathogen will illicit immune response to
multiple antigens
•Antibody demonstration
–Agglutination
–Precipitation
–Complement fixation
–Hemagglutinationinhibition
–Neutralization
–ELISA

24. •If antigenic component is identified in-vitro or
in-vivo assays can be done.
•If immunity is associated with cell mediated
immunity
–Skin tests for delayed hypersensitivity
–In-vitro tests for Cell mediated immunity
Measurement of immunity