Cross-dressers turn on T cells

摘要

As their name suggests, antigen-presenting cells flag up the presence of foreign molecules (antigens) to killer T cells of the immune system, triggering the appropriate immune response. The cells generally acquire antigens in one of two ways: by direct presentation, in which the cell itself is infected with the antigen it presents; and by cross-presentation, in which the presenting cell engulfs components of an infected cell and then processes and presents the associated antigen. A third mechanism - cross-dressing - has also been postulated~(1-3), in which an antigen-presenting cell acquires the requisite processed antigen directly from another infected antigen-presenting cell. On page 629 of this issue, Wakim and Bevan~4 report the strongest evidence yet for the relevance of cross-dressing, showing in mice that this process is required for an effective antiviral response.