And although researchers once thought that the fetal immune system would readily accept foreign cells, they now know that it is not that simple. (science.sciencemag.org)
The researchers stuck the nanoparticles to the bacteria with antibodies, which are small, Y - shaped proteins that the immune system uses to identify foreign cells, viruses and harmful bacteria. (scientificamerican.com)
But in males, as sperm only appear at puberty, they may be mistaken for foreign cells by certain elements of the immune system. (sciencedaily.com)