It is impossible to exactly define what intelligence would be in a molecule or complex molecular system. The Turing test is used to determine if a machine can match the intelligence of humans, but is inexact. Can we think of a version of a Turing test to consider if hepatitis D virus, the smallest human virus, is intelligent. For the details of hepatitis D virus' very complex lifestyle please refer to the previous post Smallest Human Virus – Very Dangerous, Very Intelligent

Small lining cells along the border of the brain’s ventricles are the gateway and supervisor of the relationship between the brain and the rest of the body, including the immune system. The choroid plexus cells produce cerebral spinal fluid, which bathes the brain and provides a cushion. But, it, also, performs a vast amount of other much more complex functions. The fluid filled ventricles are a critical source of sophisticated communication between brain and immune cells.The