The adaptive immune system, also known as the acquired immune system or, more rarely, as the specific immune system, is a subsystem of the overall immune system that is composed of highly specialized, systemic cells and processes that eliminate or prevent pathogen growth. Acquired immunity creates immunological memory after an initial response to a specific pathogen, leading to an enhanced response to subsequent encounters with that same pathogen. Like the innate system, the adaptive system includes both humoral immunity components and cell-mediated immunity components.The major functions of the acquired immune system include the recognition of specific "non-self" antigens in the presence of "self", during the process of antigen presentation, the generation of responses that are tailored to maximally eliminate specific pathogens or pathogen-infected cells, and the development of immunological memory by a signature antibodies or T cell receptors.