Cellular Immune Function in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

Area of Science:

• Immunology
• Infectious Diseases
• Clinical Medicine

Background:

• Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex condition with unknown causes and no diagnostic markers.
• Many ME/CFS patients report symptom onset after infection, suggesting immune system involvement.
• Previous peripheral immunity studies in ME/CFS have yielded inconsistent results.

Purpose of the Study:

• To investigate immunological differences in ME/CFS patients compared to healthy controls and Multiple Sclerosis patients.
• To examine herpes virus serological status and immune cell populations (T cells, B cells, NK cells, monocytes) in ME/CFS.
• To identify potential immunological biomarkers or altered immune states in ME/CFS.

Main Methods:

• Analysis of blood samples from 251 ME/CFS patients (including severely affected), 107 healthy controls, and 46 Multiple Sclerosis patients.
• Investigation of seroprevalence for six human herpes viruses.
• Flow cytometry analysis of T cell, B cell, NK cell, and monocyte populations, including *in vitro* NK cell responsiveness.

Main Results:

• No significant differences in herpes virus seroprevalence between ME/CFS and healthy controls.
• No differences in NK cell numbers, subtypes, or function between ME/CFS and controls.
• Altered T cell populations in ME/CFS: increased effector memory CD8+ T cells, decreased terminally differentiated effector CD8+ T cells, and increased mucosal associated invariant T (MAIT) cells, especially in severe cases.

Conclusions:

• ME/CFS is associated with distinct alterations in T cell immunity, particularly in severely affected individuals.
• These immune changes may relate to ongoing/recent infections or increased future susceptibility.
• Longitudinal studies are required to establish causality and explore potential immuno-modulatory treatments for ME/CFS.