Abstract
The immune system consists of several kinds of cells and molecules whose complex interactions form an efficient system for the protection of an individual from outside invaders and its own transformed cells. Innate immunity refers to the immediate antimicrobial response that occurs regardless of the nature of the invader. The adaptive immune system, on the other hand, mounts specialized immune responses to protect the individual against foreign cells from specific invaders or even tumorigenic cells, and provides long‐term protection from subsequent exposure to these foreign cells. Antibody production and cell‐mediated responses are the two interconnected branches of the adaptive immune system. Antigenic peptides displayed on the cell surface usually activate the cellular immune response. The transporter associated with antigen processing (TAP) plays a key role in the peptide‐processing and ‐presentation pathway. This Review discusses the latest progress in the structure and mechanism as well as the diseases arising from dysfunction of the TAP complex.