The immunodefence

Immunity

"Together of the mechanisms of defence of a living organism against the foreign agents (or antigens), in particular infectious." 

It should be noticed that any molecule, any cell, any body not-recognized by our defenses is immediately regarded as dangerous and thus to eliminate. This immunity is expressed by cells and can take 2 ways: one specific, the other not-specific one.
The implied cells all are resulting from a cell-mother who will give different "branches" for each immunity.

Specific immunity

·         It can be with mediation known as "humorale", or with mediation known as "cellular". Whatever the way chosen, the initiating cell of the specific immunizing answer is the T4 lymphocyte (or auxiliary lymphocyte or "helper").

·         The term "mediation humorale" is a legacy of the past, time when one took the body liquids for "moods"; it means that immunity borrowing this way will be expressed preferentially by the means of particular cells, them plasmocytes, which secrete antibody  (molecules poured in compartment  considered and "floating" in this compartment). It is also this immunity which ensures the role of memory of the immune system (at the time of the passage of an antigen, certain cells, the lymphocytes B report, remain in waking state; if the antigen is represented, they will be very quickly ready to be transformed into plasmocytes).

·         The cellular mediation is complementary to the mediation humorale. It is about an immunity expressed preferentially by the means of other cells, them T8 lymphocytes and NK (for  Natural Killer, "killers natural").

·         These two immunizing mediations are known as specific because they are set up ONLY for only one kind of aggression (for example, if the virus of influenza  contaminates an individual, an anti-virus immunity grippal will be set up and only that one) with an aim of saving the resources of the body and to be most precise possible in the fight against this aggression (this is why it exists for example several vaccines against very nearby microbes: an immunity against one will not be inevitably active against the other).

·         The recognition of the antigen being very precise, if this one transfers, the body will not be inevitably any more able to recognize it. One thus needs in complement a coarser immunity, which is satisfied with a "binary" recognition (belongs to oneself / does not belong to self) from where the interest of not-specific immunity.

Not-specific immunity

§         This immunity is much less precise in its recognition of the foreign body: it includes/understands cells (in particular them macrophages  and them polynuclear), but also natural barriers of the body (in particular skin and mucous membranes).

§         Whereas not-specific immunity is innate (our skin protects everyone about identically), specific immunity, it, "is learned" with the passing of years: it is related to our personal history and is thus almost different for each one among us. For this reason it was also called "acquired immunity".

It is with it that vaccination is interested: it does not consist in fact that "to educate" acquired immunity so that it is ready to intervene as soon as possible the day when the antigen is really presented (it is a kind of "simulation").

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