Recent studies indicate cells transfer between fetus and mother during
pregnancy and can persist in both decades later. The presence within one individual
of a small population of cells from another genetically distinct individual
is referred to as microchimerism. Naturally acquired microchimerism has recently
been investigated in autoimmune diseases, including scleroderma, thyroiditis,
primary biliary cirrhosis, Sjögren syndrome, systemic lupus, dermatomyositis,
and neonatal lupus. Iatrogenic chimerism has been investigated in transplantation
and following blood transfusion. Considering findings of naturally acquired
microchimerism along with iatrogenic microchimerism suggests microchimerism
can have detrimental and/or beneficial effects in both settings. Recent identification
of tissue-specific microchimerism either from naturally acquired or iatrogenic
microchimerism (eg, cardiac myocytes) raises the possibility that microchimerism
can be a target of autoimmunity or alternatively contribute to tissue repair.
Advances in this new frontier of research with varied and numerous implications
for human health are summarized.