Joined: April 2005
Charlie neatly sums up one of the arguments for intelligent design, which is argument from ignorance. He has used this argument almost exclusively in his discussions on talk.origins and at the Panda's Thumb. The bottom line is that Charlie cannot possibly see how microglia could have arisen to respond to brain injury, and thus invokes an intelligent agent.
There are over a thousand papers on the activation of microglia after injury, and theri behaviour is well-characterized. They respond to cytokines released by damaged brain tissue (such as the interleukins), which causes them to change their behaviour. This is no different in prinicple from the activation of a variety of blood cells after injury.
We do not know every detail about how inflammatory responses evolved, although there are plenty of clues out there. In fact, if Charlie took the time to read the literature on neuroinflammation, he might come up with some ideas himself. But that's too much like hard work, right? FAr easier just to sit back and say it was designed.
As a final thought, I challenge Charlie to write to the authors of the paper he cites and ask them whether they agree with his thesis. I will be interested to see their reply.