Neatest analogy of the week (so far)

 
And just in my own reading.  This form the NY Times about how Beta amyloid in the brain, which builds up hard plaque around neurons, and was long suspected as a cause of Alzheimer's, might actually be an immune reaction, and the A-beta (s it's called) an infection fighter, which leaves the plaque as a consequence of fighting actual infection or the possibility of it. 

In the past, Dr. Relkin said, scientists assumed “that the pathology was the plaque.” Now, he likens removing plaque to...