All naive B-cells are different
only one out of this bunch that will bind to
a particular foreign antigen.
When an antigen first appears only a few B-cells can bind; if they bind it
creates a signal transduction reaction which leads to this cell being induced
to divide into a whole population of cells called
They only recognize that particular antigen now and out of the whole
population there are two types: plasma B-cell and memory B-cells
which stay in circulation for a long time.
It takes about ten days to two weeks to get to this population.
Antibodies are tetramers with a short chain called the
and a long
chain called the
. There is a variable region that changes in
different antibodies and a constant unchanging region.
FC region = fragment crystallisable region.
Antibodies: are immunoglobulin NOT
protein families which are composed
of four polypeptides with two long heavy chains and two short light chains.
Two ‘arms’ can bind two antigens and
if you bind two you can get a
complex put together and antigens can clump together which is known as
After agglutination phagocytes (macrophages which means big
eaters or dendritic cells [discovered at McGill]) can easily engulf the
Natural killer cells (NK lymphocytes) destroy the cells marked with
antibodies which recognized the FC side so it knows that it has been
marked by an antibody which means it is invaded.
It makes a protein caused perforin (looks like tin can) and
puts a hole in the cell killing it where calcium is involved.
“The First Cut is the Deepest”
There is an activation of complement which is a cascade reaction. The binding leads to
activation of complement proteins which assemble to form a ‘LEGO donut’ to puncture the
The humoral response works after detection the foreign antigen by antigens
provided by a B-cell, but they do not actually kill the pathogen.
The binding leads to activation of complement and subunits assemble into a donut
to make a pore in the membrane of the invading cell and it will die.
Phagocytosis is where a macrophage engulfs after agglutination response.