B cells and T cells are both types of white blood cells that play a crucial role in the immune system of the human body.

B cells are responsible for producing antibodies, which are proteins that help to identify and neutralize foreign invaders such as bacteria and viruses. When a B cell recognizes a specific antigen (a unique marker on the surface of a pathogen), it will produce antibodies that specifically target and bind to that antigen. This binding triggers a series of events that help to eliminate the pathogen from the body. B cells are also able to remember the antigen so that if the body encounters the same pathogen again, the B cells can produce more antibodies quickly to fight off the infection.

T cells, on the other hand, play a more diverse role in the immune system. Some types of T cells (such as helper T cells) help to activate and coordinate other immune cells in response to an infection, while others (such as killer T cells) are directly involved in destroying infected cells or cancer cells. T cells are also important in regulating the immune response to prevent damage to the body's own tissues.

Together, B cells and T cells form a complex and dynamic immune system that is able to recognize and respond to a wide range of pathogens and other foreign substances. Understanding how B cells and T cells function is essential to developing effective vaccines and treatments for infectious diseases, autoimmune disorders, and cancer.