Acquired immunity
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Immunity we acquire as a result of Infection/ Vaccinaion
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Acquired immunity
- 1. Dr.Riyaz Sheriff M.D ….
- 3. ACQUIRED IMMUNITY • Immunity which a person acquired during his lifetime • Not related to innate immunity
- 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 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.
- 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 • Parenteral doses given with adjuvant to increase humoral immunity
- 12. 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
- 13. 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
- 14. 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
- 15. 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
- 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 – Rx of 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 Lepromatous Leprosy
- 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 – Hemagglutination inhibition – 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