A helpers' guide to infection

摘要

Killer T cells were thought to patrol the body unhindered, freely gaining access to sites of infection. But it seems that, at least in some body tissues, helper T cells must pave the way for killer T-cell entry.rnCytotoxic T lymphocytes (CTLs) are the killer white blood cells of the immune system, having crucial roles in the defence against a range of viral, bacterial and parasitic infections. During microbial colonization at peripheral body sites, such as the outer layers of the skin and mucosal epithelium, circulating CD8~+ CTLs (cells that carry a CD8 receptor molecule on their surface) exit from blood vessels to access and destroy cells harbouring pathogens.