Naturally failing immune systems and naturally overactive immune systems have been blamed as noninfectious causes of chronic disease. But does it make sense that evolution would have generated such a complex system of checks and balances if these complexities were only to generate the system’s downfall? Imagine making an extravagant security guard system that self-destructs without provocation. We would not expect people to select the ineffective complex system over a more effective simple system. If an extravagant immunological security system self-destructed, then natural selection similarly would favor the simpler system. The more extravagant system wouldn’t be reproduced. We can expect that natural selection will not favor added complexity to immunological security systems when the increased complexity destroys the body without provocation. The immune system may, however, be driven to self-destructive tendencies through the ever-changing strategies of the burglars it is attempting to deter. Streptococcus pyogenes, for example, may damage the heart because one of the germ’s proteins has evolved camouflage that makes it look so much like a protein on the human heart that the immune response against the bacteria attacks the heart. In the absence of such provocation, though, the immune system is the quintessence of efficiency and flexibility.*22\225\2*
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