Mucosal HIV transmission

Sexually transmitted HIV begins its battle with the immune system in the mucosal tissues of the host gut. Sun et al. (page 705) now recapitulate these events for the first time in a small animal model by replacing a mouse immune system with human lymphocytes.

Mice that lack their own T and B lymphocytes can be humanized by grafting them with human bone marrow, fetal liver, and fetal thymic tissue (BLT). This environment supports the development of human stem cells into various immune cell lineages, but it was not yet clear whether the cells were fully functional and homed to the appropriate tissues.

Sun and colleagues now use this system to show that human lymphocytes, including CD4⁺ T cells expressing the HIV coreceptors CCR5 and CXCR4, are able to migrate into...