Immune modulators is a broad term used, but amongst the cfs/me experts this mostly refers to substances such as ampligen and immunovir which appear to work through their interferon inducing effects. Interferon itself has antiviral properties but is also known to increase nk function.
Russia and other eastern block countries in the 1960s and 70s discovered/invented many interferon inducers to try and treat the many viral infections that didnt have many treatments available at the time, from the cold virus to hep B/C to different herpes viruses and were shown to have some positive effects.
I also believe that they were also used with and also after treatment with traditional interferon treatments as they found that with interferon treatments, that there was some negative feedback issues ie they werent producing their natural interferon as well as previously before the use of interferon drugs. Interferon inducers helped avoid this situation by stimulating the patients own interferon production.
In regards to ebv infections, they have found that this virus can avoid the immune system by somehow turning down the bodies own interferon production, this reduces the actions of the immune system on fighting these types of infections.
So those with the ability to think with a broad mind and not a narrow view, would notice that cfs experts especially in the research on nk function in cfs/me such as Dr Nancy Klimas and co recommend immunovir for its effects on nk cells and Dr Peterson also, as well as his experience with ampligen, but ampligen is restricted to many due to cost. Dr Chia has had success in using herbal immune modulators to treat chronic enteroviral infections, i assume due to their effects on interferon, as he uses this as an alternative to the drug interferon itself as it can be a hard drug to tolerate and is also expensive. So it appears Dr Chia has found a link between fighting infections in cfs/me and immune modulators that work on inducing interferon naturally.
SO i guess the concept of immune modulators seems psychobabble amongst those that believe that infections have nothing to do with cfs/me, even though the concept of infections in cfs/me hasnt been unproven. Since the concept of ME has began, the weight of evidence leans heavily towards some type of infectious involvement, be it a trigger or a chronic infection/s, along with some type of immune dysregulation. To call it a coincidence, would be very naive. The psychobabblers seem to be the ones who deny evidence of research over the last 50 yrs or so even though this research has been heavily stifled by lack of funding. I am amazed at the lack of lateral thinking amongst some of the green practioners entering into this field with total ingorance of what has gone on before them in the cfs/me field, which shouldnt be ignored, but this is due to their narrow point of their own view with their blinkers on.
Im also amazed that nurofen has been mentioned a few times as some type of treatment for ME(symptom management sure but its still not very effective for many of us), and that other treatments that many patients have used for treating infections is brushed aside as a fluke as cfs is an up and down illness, so one probably took the treatment when they were in the upswing of a good spell. Its never taken into account that the patient has tested these treatments out numerous times and can see the pattern of the treatment working and or that those treatments over the long term can improve outcomes even with the ups and downs, as the downs become less so and less frequent and the ups increase. Then some find they regress quickly once they stop a certain treatment. The above is repeated several times. That does not appear to be a fluke to me, its not a hardcore experiment but we have little going on in the big picture doing research for us, so we are forced to find things that work for us.