The tests showed lower levels of immune molecules in those with atypical CFS than in those with the classical variant. The analyses revealed drastically lower levels of interleukin 7 (a protein that plays a key role in the adaptive immune response to infections), interleukin 17A, and chemokine ligand 9 (molecules with a key role in the adaptive immunity to neurological illnesses).
Additionally, these biological features were accompanied by different trajectories of disease history and comorbidities. Those with atypical CFS tended to have a history of viral encephalitis and tended to fall ill after traveling abroad or receiving a blood transfusion. Furthermore, people with atypical CFS went on to develop simultaneous conditions such as seizure disorders, several types of cancers, or demyelinating disorders - that is, multiple sclerosis-like diseases that damage myelin, the protective sheath around the nerve cells in our brains and spinal cords.
Overall, both atypical and classical CFS patients were revealed to have an abnormal immune system when compared with the general population.
However, only people with classical CFS displayed the previously discovered 3-year mark of CFS - namely, after 3 years of having an "overzealous" immune system, CFS patients show signs of immune "exhaustion," with dramatic drops in their levels of immune molecules.