Dr.Riyaz Sheriff M.D ….

IMMUNITY IMMUNITY

INNATE

NON SPECIFIC

SPECIES

RACE

INDIVIDUAL

SPECIFIC

SPECIES

RACE

INDIVIDUAL

ACQUIRED

ACTIVE

NATURAL

ARTIFICIAL

PASSIVE

NATURAL

ARTIFICIAL

ACQUIRED IMMUNITY

• Immunity which a person acquired during his

lifetime

• Not related to innate immunity

Acquired IMMUNITY

ACQUIRED

ACTIVE

NATURAL ARTIFICIAL

PASSIVE

NATURAL ARTIFICIAL

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

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.

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

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

natural active IMMUNITY

Bacterial infections provide with less degree of

immunity

PREMUNITION – Seen in syphilis . The immunity to

reinfections lasts only till the original infection is

active.

Chancroid does not provide the person with any

immunity . Person may develop lesions following

reinfection even when original infection is active.

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

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

• Parenteral doses given with

adjuvant to increase

humoral immunity

Passive immunity o No infection

o Readymade antibodies are administered

o No latent period

o No negative phase

o Immediate protection

o Immunity lasts for short duration till antibodies are metabolized

o No secondary response

o Passive immunity decreases with repetition

Types of passive acquired immunity

PASSIVE

NATURAL ARTIFICIAL

Resistance transferred from mother to baby

Via placenta

Breast milk – colostrum – IgA

IgM production by fetus can start from 20th 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 toxoid during pregnancy

Types of passive acquired immunity

PASSIVE

NATURAL ARTIFICIALResistance transferred by

administration of antibodies

Hyper immune sera

Convalescent sera

Pooled human Ɣ globulin

Used for prophylaxis and therapy

Hyperimmune sera

• Anti-tetanus serum (ATS)

• Prepared from hyperimmunized horses

• Temporary protection

• Disadvantages • Hypersensitivity

• Immune elimination

• In use – Hyperimmune globulin of human origin

Animal origin in use

Anti-Gas gangrene sera

Anti-Botulinum sera

Antivenoms

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 – Rx of patients with immunodeficiencies

Indications for passive immunization

• Immediate and temporary protection of a

person at risk of developing infection

• To arrest overactive active immunity

Eg. Rh incompatibility

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

Adoptive immunity

• Special type of immunization

• Injection of immunologically competent

lymphocytes TRANSFER FACTOR

• Tried in treatment of Lepromatous Leprosy

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

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

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

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

– Hemagglutination inhibition

– Neutralization

– ELISA

• 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

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