To stimulate discussion about haptens :
Clonal selection : cell competition for food
<snip>
In the following story, let's examine the effects of this translation :
lymphocytes are depicted as diverse animals in a natural reserve, and
antigens as diverse food. The story illustrates that clonal selection,
leading to proliferation of the most efficient antigen-binding cells, might
be interpreted as a competition between specialized predators for access to
alimentary resources.
Mr Antigensignalling : The zoo director wants our research group to
determine exactly which food is the best for each animal in the reserve. As
food capture is a complex recognition and signaling system, we should take
one individual of each animal species in the reserve for complete molecular
dissection. Using detailed description of teeth, especially within frozen
aliment-teeth complexes*, digestion mechanisms, 3D structural models and
molecular design, we will surely determine how each specific food acts on
the reproduction of each specific animal.
Mr Antigenfood : That is a great idea. It will convince the zoo director to
buy a new powerful computer. So we can play the last flight simulator.
Mr Antigensignalling : Are you crazy ? We have a huge repertoire of billions
of rapidly reproducing and evolving animals in the reserve. With such a
diversity, we will have huge calculation needs to reconstitute every
molecular details.
Mr Antigenfood : Don't worry, Sig. The experiment is already ongoing without
the computer. First, I have asked to reduce the overall feeding in the
reserve. Then, every week, we provide only one kind of food. The animals
will compete for the food. At the end of the week, we just count the
animals. The animals who have the best capture and digestion efficacy for
the food will be for sure the most activated and reproductive in the
reserve. The less efficient animals have no access to the food. They just
sleep and are not able to reproduce.
Mr Antigensignal : Good idea ! And to make the animal reproduction and
activity more detectable, why don't we use food adjuvants ? Let's attach the
food to a big energetic molecule. **
* refer to crystals of antigen-antibody complexes.
** Immune response is more efficient when the antigen is associated to a
molecule called adjuvant. In an extreme situation, small molecules (haptens)
are not able to induce an immune response if they are not coupled to a large
protein (carrier) (see ref. 12 for a review). As the hapten is able to
interact specifically with the specialized antigen receptor, it remains at
present unclear within the signal-triggering representation why it is not
able to cause cell proliferation and activation when alone. This might be
more easily understood if lymphocyte proliferation does not require a
signal, but a metabolic advantage provided by the antigen as a nutritive
resource. The carrier molecule might thus constitute a metabolic resource
absent from the hapten.
(full text at : http://www.heraclitean.com/hbg/essays/immunometab_sonigo/)
Pierre
Tyson <tyson at canada.com> a écrit dans le message :
q7YY3.67944$it.1671737 at news2.rdc1.on.home.com...
> that's why haptens are called haptens and not antigens....
>> ...haptens are too small to illicit an immune response...small organic
> molecules or metals are too small to be recognised and therefore require a
> carrier protein to bring about an adaptive response
> ....haptens cannot recruit T-cell help...but the addition of a
> chemicaly-linked carrier protein allows the priming of T-cells with
peptide
> from the carrier
>> <Jenfromwcu at AOL.COM> wrote in message news:0.5fa1cde4.2564a927 at aol.com...> | Why do haptens need a carrier protein? Why can't they elicit and immune
> | response themselves?
>>
