The role of B cells in the immune system is crucial for the adaptive immune response. They are a type of white blood cell that produces antibodies to identify and neutralize pathogens like bacteria and viruses. Upon encountering an antigen, B cells can differentiate into plasma cells that secrete specific antibodies, leading to the destruction of the pathogen. Additionally, some B cells become memory cells, allowing for a faster and more effective response to future infections by the same invader.