It’s a membrane Ig (IgM), associated glycoporotein, Ig α and Igβ , which has a moderately large cytoplasmic
domain. These domains each include a short region important for transmitting a
signal indicating antigen has bound. This region is called immune tyrosin based
activation motif ( ITAM ).
Functions of BCR complex
On activation by antigen, B cells differentiate into plasma
cells producing antibody molecules of the same antigen specificity as the receptors.