How is immunological memory established?

When a pathogen enters the body's bloodstream or tissues, antigen-presenting cells (APCs), which are a type of immune cell, identify the pathogen as foreign and digests it. Subsequently, these APCs have antigens specific to the encountered pathogen on their surfaces and present them to T cells. This interaction triggers the activation, differentiation, and proliferation of T cells. Upon initial exposure to a pathogen, naive T cells transform into effector T cells. They are capable of initiating a rapid and effective immune reaction against the foreign substance. Among these effector T cells, helper T cells aid in coordinating the immune response, while cytotoxic T cells directly eliminate infected cells. Helper T cells assist B cells in producing antibodies to target pathogens and generate memory B cells for future encounters. After the pathogen is eliminated, the majority of effector T cells perish, leaving behind long-lasting memory T cells.