What is the main role of plasma cells in the immune system?

The primary role of plasma cells in the immune system is to secrete antibodies. Plasma cells are differentiated B cells that arise following the activation of B cells in response to an antigen. Upon encountering a specific pathogen, B cells undergo a transformation into plasma cells, which are specialized for the production of high volumes of antibodies.

These antibodies are critical components of the adaptive immune response, as they bind to antigens present on pathogens, neutralizing them and marking them for destruction by other immune cells. This mechanism enables the immune system to specifically target and eliminate invading pathogens. Additionally, the antibodies produced by plasma cells can provide long-term immunity, as they remain in circulation and can act quickly upon subsequent exposures to the same pathogen.

In contrast, other options do not accurately reflect the main function of plasma cells. While they are important for the immune response, producing memory cells, directly attacking pathogens, and stimulating T-cells are roles associated with different components and processes of the immune system. Thus, the secretion of antibodies is indeed the defining characteristic of plasma cells.