Invisibility of Tissues and the Mother/Fetus Paradox: An Hypothesis*
Abstract
How do tissues hide themselves from the body's natural defense system? Anonymity is difficult to sustain in the blood stream. Almost all surfaces become tagged by polyionic molecules, such as proteins, within milliseconds of being exposed to plasma (which, after all, is an abundant source of animal glue). Both the tagging and the gluing are spontaneous events and result from the release of electrostatically bound water when ionic groups of the surface and the protein mutually satisfy their respective charges. The driving forces responsible for the spontaneity of the adsorption/gluing process are various attractive forces and the disordering of bound water leading to a gain in entropy. But suppose the surface of an intruder had no surface charges, causing it to resemble the surface of a slice of (bulk) water. The polyionic proteins would not find anything to tag, there is no entropy gain, there are no attractive interactions, and the interloper would be invisible.