How is B cell activated?

B cells may be activated via two pathways, one that is dependent on T cells and one that is independent of T cells.

T cell-dependent activation 

T cell-dependent activation proceeds via 3 main steps:

1. B cells absorb the antigen
2. B cells present pieces of the antigen on their surface via an MHC (major histocompatibility complex)
3. T cells recognize the antigen pieces via the MHC and activate the B cells 

T cell-independent activation 

This activation pathway can only proceed if two conditions are met:

1. The B cell must receive a signal that an attack or intrusion is taking place 
2. The B cell must encounter an antigen that it can recognize

When the B cell encounters an antigen that it recognizes, the B cell’s surface receptors bind to the antigen. This activates the B cell, triggering it to divide and differentiate into a specialized plasma cell, which produces antibodies that bind to the antigen, neutralizing it.