Final answer:
The immune system develops antibodies when it is exposed to antigens, which can be from pathogens or vaccinations, leading to the activation of B-lymphocytes and production of specific antibodies.
Step-by-step explanation:
The immune system develops antibodies through exposure to antigens. When a person is vaccinated or encounters a pathogen, antigens specific to that pathogen are introduced into the bloodstream. These antigens are recognized by B-lymphocytes, also known as B cells, which have cell surface receptors called immunoglobulins. The direct interaction between the antigens and the B cells triggers a series of events leading to the production of antibodies. These antibodies are capable of neutralizing pathogens or marking them for phagocytosis and activating the complement cascade. The production and secretion of antibodies by plasma cells mediate the humoral immune response. Adaptive immunity also forms memory cells which ensures a faster and stronger response upon subsequent exposures to the same antigen.