B cells are an important part of the immune system. One of their jobs is to neutralize the threat from a foreign invader known as a pathogen. They do this by producing an antibody that binds with the antigen on the threatening entity. 

When an antigen binds to a receptor on a B cell, the B-cell receptor signaling pathway is activated. Bruton’s tyrosine kinase (BTK) is an enzyme that’s critical to the activation of the B-cell...