> >> Why doesn't the B-lymphocyt just proliferate, after it bound its antigene?
>> >Thanks be to heaven it does not!!!
> >The B cell needs 2 (two) signals to go on with proliferation. The second
> >signal is usually delivered by T helper.
>> If the antibodies were so damn specific and all antigenes were so damn
> foreign to the organism, why thank god for the 2 <two> signals?
> Mark Ion Quest <joaccigh at w250zrz.zrz.tu-berlin.de>
1. Because it is a back-up system for the organism. There is a double
conformation: both B and T cell have to"agree" that what they both see is
non-self.
2. Because T cell will also "tell" B cell via cytokine signaling what
class of ABs to make. eg. interleukin-4 and/or -13 released by activated T
helper cell during associative recognition will cause IgE or IgG4
production by B cells.
3. Because in order to activate B cells CD40 molecule on the B cell
surface has to be activated as well and that can only happen during
cell-cell interaction, and that second cell has to express CD40 ligand on
its membrane. That second cell is T helper (usually - not always, but
that's another story).
4. Because the model of one-signal you are proposing would probably cause
either tumor (eg.multiple myeloma) or autoimmunity.
