In article (Date: 1 Jul 92 12:37:19 EDT) Nathan Maman (maman at titan.Colorado.
EDU) writes:
> I'm not an immunologist myself but I once read something about the
>self/non-self recognition. It was in a book written in '71 by Jacques
>Monod ``Hasard et neces site''. I think in english it should be ``Luck and
>necessity'' or something like that.
> As far as I remember well, he said in this book that the defense cells
>cannot``learn'' new types of ``strangers''. The process was described as the
>cell always trying to produce every antibody it knows. That is an explanation
>for different people having different capabilities concerning this subject of
>self defense. Also perhaps for auto-immune responses.
That's right. In B cell development, potentially all antibody specificities
can be made. Be cells are not 'instructed' to make certain specificities,
although I think that is what was taught in the mid 50s to early 60s (thus the
instructional theory of immune response).
> When the antibodies produced are unused, ie have not met the body
they match, the production is lowered.
Right again. If a B cell makes a useless antibody specificity then that cell
has is not maintained ie. brought into the expanded repertoire. Unless there
is some other reason such as idiotypic connectivity.
> And if on the contrary they matched
something
>then the production is increased. But the increase rate may be not high
enough
>to insure a good defense. That's why, according to me, there is a
``training''
>for cells.
This is where the topic gets the most attention. Self antigen is around all
the time. Therefore a system is needed to tolerize self reactive B cells and
this is where the 'S' word gets used, and systemic/peripheral tolerance.
*** suppressor cells***
The various antibody specificities to any one particular foreign antigen are
selected for expansion based on the relative avidities for the antigen. High
avidity B cells are selected first and lower avidity lost (classical B cell
selection).
I think what Coutinho is trying to say is that self/non-self descrimination
cannot occur at the level of Ig gene rearrangement (antibody specificity)
and that there are other 'levels of organization' where B cells are trained
to be tolerant or can respond to a given antigen and this occurs (and may be
different) for the systemic and pheripheral immune system.
Sincerely,
Greg
gdenomme at uwovax.uwo.ca
Dept. Microbiology and Immunology
University of Western Ontario
London, Ontario, CANADA
