Final answer:
B lymphocytes, or B cells, primarily function to secrete soluble antibodies that help identify and neutralize pathogens. They are activated by antigens which they engulf and present to helper T cells, leading to their differentiation into antibody-producing plasma cells and memory B cells.
Step-by-step explanation:
The main function of B lymphocytes, also known as B cells, is to secrete soluble antibodies. These antibodies are Y-shaped proteins that play a crucial role in the immune system by identifying and neutralizing foreign invaders, such as pathogens. B cells become activated through a sequence of events beginning with the engulfment and digestion of an antigen, after which they present it on their MHC to a helper T cell. This interaction leads to the B cell receiving signals, often in the form of cytokines, from the activated T cell. Subsequently, B cells multiply, and their daughter cells differentiate into plasma cells and memory B cells.
It is the plasma cells that are responsible for antibody production. In contrast to B cells, T cells do not produce antibodies but have various functions in cellular immunity, such as secreting factors for communication with other immune cells and destroying cells infected with intracellular pathogens.