B cells are one of the major cell classes responsible for adaptive immunity, the branch of the immune system that develops and recognises pathogens and develops its resistance to them. B cell production in the body is vast. We produce almost a billion of them a day! As the B cells develop, and before they make their way out into the body, they begin to manufacture several distinctive proteins that are bound within their membrane. These proteins function as antigen receptors, capable of recognising specific antigens recognised as foreign and that provoke immune responses.
How are B cells activated?
The way B cells are activated and play their role is fascinating.
- The B cell receptors bind to antigens. These antigens may be circulating, but most often are delivered by antigen-presenting cells such as macrophages
- Some of the antigen is then taken into the B cell, where it is broken into fragments, and then combined with MHC
- The antigen fragment/MHC combination is then displayed on the outside of the B cell
- At this point, another group of cells, the T helper cells will recognise the antigen/MHC combination, and start to communicate with the B cell displaying it
- This communication then allows the B cells to proliferate and differentiate. B cells can differentiate (morph and change) into plasma cells
- Plasma cells secrete antibodies to the antigen. These cells differentiate at an astounding rate and a few days after exposure to an antigen, there is a clone army of plasma cells secreting hundreds of millions of antibodies