A number of drugs which act on the body's immune system (immunomodulatory drugs) have been suggested as possible forms of treatment for sub-groups of people with ME/CFS. These drugs include Ampligen, immunoglobulin, alpha interferon, inosine pranobex/Imunovir and tumour necrosis factor alpha inhibitors. Unfortunately, the results from clinical trials so far have failed to demonstrate any really consistent and significant benefits. So most doctors in the UK do not use immunomodulatory drugs for people with ME/CFS.
A report in BMC Neurology (July) describes how three people with ME/CFS (one of whom had Hodgkin's disease) experienced a significant degree of improvement during and after the use of two drugs – rituximab and methotrexate –that depress what is called B cell function.
The authors of this paper suggest that there could be a sub-group of people with ME/CFS where immunomodulatory drugs that modify B cell numbers and function could be an effective form of treatment.
http://www.biomedcentral.com/1471-2377/9/28 along with a link to the full paper.