in addition to the points recently made re aging as result of defences
against cancer ...
i've felt that the immune system is optimized (like many other systems)
for optimal reproductive efficiency (i.a.). maybe the lower limit to
immunosurveillance is the threat of cancer, and the upper limit is set
by the treat of autoimmune diseases. a wise body will have as high an
immunosensitivity as is compatible with an acceptable risk of death
from an autoimmune disorder.