It's obvious that mother and baby share a lot in common. On the immune system level, the sharing is extremely deep. You may have heard that mothers will share their antibodies with their babies: there's even a receptor in the baby's gut that will grab the antibodies from milk and pull them into the bloodstream. And that immune cells called natural killer cells that normally destroy invading organisms play a major role in carving channels through the placenta so the fetus and mother can be connected.
The new finding in this vein is that Mom actually donates T cells to the baby. You can detect maternal T cells (called Tregs for "regulatory") in the baby's lymph nodes. It seems a regiment of maternal Tregs marches across into the baby because those cells have already been trained to find "bad cells" and leave "good cells" alone. Rather than have the baby learn all this anew, the mother's cells serve as teachers that can regulate the baby's immune system.
On a philosophical level I find the fluidity of identity between mother and son fascinating. Not only do all his mitochondria come from his mother, so do some of his early Tregs. There is actually a little bit of her crawling around in him, teaching him ... although his body is clearly fully his!
On a theological level this resonates with Paul's theology, because he too presupposes that our identities are fluid. According to Paul, we are all part of each other, sharing on a deeper level than we know in the church, bearing one another's burdens, because we are one in Christ. (Think of how Laurie's family suffered, and how we went to a memorial service to suffer with them.) Those 5 words "we are one in Christ" are quick to say but contain depths of meaning. We are a body with Jesus as the head. We have died in Christ, we live in Christ. What he did is given to us, and his spirit powers our life and teaches us day to day on what to do and what not to do. Paul seems to have no problem with Jesus doing something and it applying to us, or with Jesus living inside us -- that's fluid identity. Jesus in my heart, momma in my lymph nodes.
There's a lot here that I'm still unpacking, but the fundamental image -- bits of the mother intergrated into the son, teaching him and protecting him -- is the important thing right now. That and how "Christ in you" is dependent on the same kind of fluid identity.
Does this bring anything to mind for you? Other situations or metaphors or verses? Or does it not work? What are the limits to this analogy?