What is a B cell receptor?
A B cell receptor is almost exactly the same as the antibody for that cell. The B cell rearranges its genes to make a unique immunoglobulin gene combination and this will initially encode the B cell receptor on the surface of the cell.
The specificity of the B cell receptor guides the development of the B cell, when antigen binds to it, it causes signals to be transmitted into the cell. If the signals arrive at the correct strength with the correct degree of signaling from other molecules (triggered by other helper cells), then the B cell matures and may eventually become a plasma cell which is like a factory to produce antibodies. The antibody is encoded by exactly the same gene rearrangements, but is secreted outside the cell instead of being fixed to the surface. Check out the positioning of the antibody in the cartoon below.
Because the development of the cell is guided by the specificity of the B cell receptor, then when the B cell reaches the end of its development and becomes a plasma cell the antibody has all the characteristics that were “chosen” in the B cell development process.
Figure from: The ageing human B cell repertoire: a failure of selection? Clinical & Experimental Immunology Volume 183, Issue 1, pages 50-56, 6 OCT 2015 DOI: 10.1111/cei.12700 http://onlinelibrary.wiley.com/doi/10.1111/cei.12700/full#cei12700-fig-0002
Faculty of Health and Medical Sciences, Duke of Kent Building, University of Surrey,
Guildford, GU2 7XH