Chuckles, recent (July 2014) scientific paper extolling anti inflammatory effects of EPA / DHA: "having potent anti-inflammatory and immunoregulatory actions at concentrations in the nanomolar and picomolar range."
So because they find it active at the nanomolar and picomolar range there must be hvery high affinity receptors sitting on cell services.
Remember, DHA is good, but DHA is hard to take in high dose, whereas EPA is similar to placebo - so big difference at high dose.
It reads The mechanisms by which such effects are exerted is still a matter for controversy, but it seems likely that oxygenated metabolites derived from eicosapentaenoic acid (20:5(n-3) or EPA) and docosahexaenoic acid (22:6(n-3) or DHA), the resolvins and (neuro)protectins, must play a significant part as they have potent anti-inflammatory and immunoregulatory actions at concentrations in the nanomolar and picomolar range.