I've written up on glutamine and immune function. If you read the last study I posted they demonstrated that glutamine supplementaion will not prevent immune system depression due to exercise. But it may enhance overall immune function.

That last thing you posted doesn't show that it will help athletes, they concluded that supplementing will aid critically ill people and are making an inference that it will also aid 100% healthy athletes. Comparing athletes to people on their death beds is an apples to oranges comparison.