Immunogen & Antigen

Topics: Immune system, Antigen, Major histocompatibility complex Pages: 2 (285 words) Published: June 17, 2013
* Differentiate between Immunogenicity and Antigenicity.
Vaccinations are modified diseases.
Immunogen: any agent capable of inducing an immune response.  
Antigen: any agent capable of binding specifically to components of the immune system (lock and key)  
All immunogens are antigens but not vice versa.
High molecular weight: substances > 6000 Da are generally immunogenic From 1000-6000 -> may or may not be immunogenic.
Haptens: antigens which are not immnogens (molecular weight too low and chemically simple) Combines haptens with protein carriers to be big enough.
Chemical complexity: generally, increase complexity increases immunogenicity. Dinitrophenol combined w -something - --> combines
Degradability: b cells recognise antigens found on surface of any pathogen(proteins and non-proteins) T cells only able to recognise proteins and only able to recognise Antigen presenting cells. Enzymatic degradation of antigen is done by APC.

D-amino acids cant go through enzymatic degradation whereas the L-amino acids CAN BE. Hence vaccinations are made up of l-amino acids. Non-proteins cannot usually be degraded.
3 types of injections: intravenous ; intramuscular ; sub-cutaneous (into adipose tissues OR fats)  
BCR and TCR => b/t-cell receptor
Accesible -> found on outside of the pathogen (hence accessible)  
Adjuvants: chemicals which are added to an antigen to increase an immune repsonse Trying to say that the antigen is ALREADY ABLE to induce an immune reponse (hence haptens is not in this group) , but the magnitude is not great enough. When antigens is mixed with adjuvants, magnitude response is heightened  

Make it more obvious by precipitation of antigens by adjuvants  
Primary response: vaccinations. (first time)
Secondary response: (second time ) the response is faster as the antigen is not foreign.
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