At the clone stage antibodies do not leave the B-cells.
The abs are embedded in the plasma membrane of the cell and are
called antibody receptors.
When the receptors in the membrane recognise and antigen on the surface of the pathogen the B-cell divides rapidly.
The antigens are presented to the B-cells by macrophages
Some activated B cells PLASMA CELLS these produce lots of antibodies, < 1000/sec
The antibodies travel to the blood, lymph, lining of gut and lungs.
The number of plasma cells goes down after a few weeks
Antibodies stay in the blood longer but eventually their numbers go down too.
Some activated B cells MEMORY CELLS.
Memory cells divide rapidly as soon as the antigen is reintroduced.
There are many more memory cells than there were clone cells.
When the pathogen/infection infects again it is destroyed before any symptoms show.
Also known as immunoglobulins
The heavy and light chains are polypeptides
The chains are held together by disulphide bridges
Each ab has 2 identical ag binding sites – variable regions.
The order of amino acids in the variable region determines the shape of the binding site
Some act as labels to identify
antigens for phagocytes
Some work as antitoxins i.e. they block toxins for e.g. those causing diphtheria and tetanus
Some attach to bacterial flagella making them less active and easier for phagocytes to engulf
Some cause agglutination (clumping together) of bacteria making them less likely to spread
Mature T-cells have T cell receptors which have a very similar structure to antibodies and are specific to 1 antigen.
They are activated when the receptor comes into contact with the Ag with another host cell (e.g. on a macrophage membrane or an invaded body cell)