http://www.uptodate.com/contents/nk-cell-deficiency-syndromes-treatment Interesting. I find that its interesting where it mentions antiviral prophylaxis for virus common to cfs like ebv/cmv etc. I think if someone is negative to a retro virus but has nk dysfunction then maybe nk defiency syndrome is a sub set of cfs which would then wrap up most of the viral infections into this one sub group, also help distinguish between those who are diagnosed as 'pure' ME with lots higher neurological symptoms with brain scan abnormalities/brain injury and those with chronic viral infection with nk dysfunction. I also wonder if nk function tests arent commonly done outside research situation as this could potentially take away from the psychobabblers client base and also cause they arent real sure on how to treat it???? cheers!!!