Spontaneous fusion of cells between species yields transdifferentiation and retroviral transfer in vivo.

Human cells can fuse with damaged or diseased somatic cells in vivo. Whether human cells fuse in vivo in the absence of disease and with cells of disparate species is unknown. Such a question is of current interest because blood exchanges between species through direct physical contact, via insect vectors or parasitism, are thought to underlie the transmission of zoonotic agents.