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[[Image:Active Immunisation.jpg|thumb|right|150px|Active Immunisation - Copyright nabrown RVC]]
[[Image:Active Immunisation.jpg|thumb|right|150px|Active Immunisation - Copyright nabrown RVC]]
'''Active immunisation'''
'''Active immunisation'''
===Adjuvants===
===Adjuvants===
*Used with vaccines containing inactivated organisms which alone only stimulate a weak immune response
*Some create a depot of antigen at the injection site allowing a steady flow of antigen into the afferent lymph
*Some stimulate the immune system to amplify the adaptive immune reponse to antigens
**E.g. Pathogen-associated molecular patterns (PAMPs)
**E.g. PAMP-like adjuvants which assist naive T cell priming
*Different subtypes of T helper cells are stimulated by different adjuvants
**E.g. Aluminium salts generate bias T helper II reponses for '''antibody'''-mediated immunity
**E.g. Killed mycobacteria generate IL-12 producing good '''cell'''-mediated immunity
==Which type of vaccine is used for each disease?==
==Which type of vaccine is used for each disease?==
*The life-cycle of the organisms needs to be understood to ascertain the best type of immune reponse for fighting the particular infection
*A vaccine can be created to provide specific immunity which is best suited for fighting the specific infection
===Immunity to Virus Infection===
*The virus life cycle consists of an extracellular phase, a replicative intracellular phase and another extracellular phase spreading virual particles to other cells to begin the life cycle again
*Immunity for the extracellular phase requires neutralising '''antibody'''
**B cells needed
**T helper type II cells needed (for the MHC class II pathway)
**Live vaccine can be used
**Killed vaccine can be used
**Subunit vaccine can be used
*Immunity for the intracellular phase requires '''CD8+ cytotoxic T cells'''
**MHC class I pathway
**Only live vaccine can be used to get into cells (entering via the endogenous pathway)
===Immunity to Bacterial Infection===
*Extracellular bacterial infection need '''antibody''' production for opsonisation and to activate the complement pathways
**B cells needed
**T helper type II cells needed
*Vesicular infections can only be cured by organisms being destroyed inside '''macrophages'''
**T helper type I cells needed
==When do we vaccinate?==
==When do we vaccinate?==
*Usually when animals are young
*Breeding females so immunity is passed to offspring via the colostrum
**Protects neonates for the first 8-12 weeks of life
*Vaccination of young animals should be when the natural passive immunity decreases below the threshold for providing protection. Active immunity should then be stimulated so that the animal has constant protection. The vaccination should not be given too early, as the natural immunity can interfere with immunisation by binding and neutralising the vaccine antigens.
*2 vaccines are usually given to allow for differences between neonates as the point where natural immunity decreases and active immunity needs to be stimulated, will differ between littermates and between different animals
==Links==
==Links==