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*'''Exogenous vaccines''' are when the antigen is processed from the outside by endocytosis without any new proteins being made by the host cell
*'''Exogenous vaccines''' are when the antigen is processed from the outside by endocytosis without any new proteins being made by the host cell
**involves MHC class II processing
**involves MHC class II processing
**E.g. Inactivated and subunit vaccines
==How do we vaccinate?==
==How do we vaccinate?==
*Live attenuated organism
*Live attenuated organism
**Virulent organisms cannot be used as vaccines as they would cause disease
**Virulent organisms cannot be used as vaccines as they would cause disease
**Virulence is reduced by growing the organism in altered conditions so that it is less able to replicate when introduced to the host and therefore less likely to cause disease
**Virulence is reduced by growing the organism in altered conditions (e.g. in cells or eggs) so that it is less able to replicate when introduced to the host and therefore less likely to cause disease
**Produces a superior response to disease than using killed organisms as the dose of [[Adaptive Immune System - WikiBlood#Antigen Recognition|antigen]] is larger and more sustained
**Produces a superior response to disease than using killed organisms as the dose of [[Adaptive Immune System - WikiBlood#Antigen Recognition|antigen]] is larger and more sustained
**Virulence can also be reduced by genetic engineering
**Naturally occuring avirulent strains can also be used
**Response takes place at site of natural infection producing a greater local response than with killed organism vaccines
**Response takes place at site of natural infection producing a greater local response than with killed organism vaccines
**E.g. The current vaccine for Tuberculosis (called BCG) contains an attenuated form of a mycobacteria
**E.g. The current vaccine for Tuberculosis (called BCG) contains an attenuated form of a mycobacteria
**E.g. Vaccines for Leishmaniasis
**E.g. Vaccines for Leishmaniasis
**E.g. Vaccines for parainfluenza virus 3 of calves is developed to be temperature-sensitive so that it grows at 34 C in the upper respiratory tract but not at 38 C in the lungs
*Killed inactivated organism or toxin (toxoid)
*Killed inactivated organism or toxin (toxoid)