There is a strong association between infection-related cell-mediated immunity and autoimmune diseases such as diabetes, multiple sclerosis (MS), rheumatoid arthritis (RA) and lupus erythematosis (SLE)1. Infections have also been associated with unusual immunopathologies of unknown origin, such as Wegner granulomatosis, sarcoidosis, colitis, panniculitis, bronchiolitis obliterans and even chronic fatigue syndrome. Despite exhaustive efforts, a definitive link between one particular pathogen and any of one these pathologies has never been found. More often several pathogens have become associated with each of these conditions. For instance multiple sclerosis has been associated with Epstein Barr virus (EBV), measles virus, HHV-6, varicella-zoster virus, and Picornaviruses2-6. Panniculitis in the form of erythema nodosum and bronchiolitis obliterans have both been associated with unusual cell-mediated immune responses that occur following non-specified viral or intracellular bacterial infections 7-9. Erythema nodosum, which has also been associated with Crohn’s disease8, is a very painful condition, where nodules of inflamed subcutaneous fat often on the shins and forearms persist for months. There is no known therapy. Bronchiolitis obliterans is a lethal condition in humans where the bronchioles become occluded with immune cells and fibrinous material, with no known cause or treatment9.
Chronic fatigue syndrome (CFS) is another unusual multisystem disease which is thought to be associated with immune dysregulation. Over the past two decades millions of patients world wide have suffered from a clinical syndrome of disabling fatigue, myalgias, palpitations and cognitive dysfunction that lasts longer than 6 months. In 50% of cases it develops after a mild viral illness. Cases may appear sporadically or in clusters10,11. Many attempts have been made to define the syndrome on the basis of an etiologic agent. These agents have included Epstein-Barr virus10, Brucella12, Candida albicans13, Borrelia burgdorferi, and human herpesvirus-614,15. More recently it has been associated with enteroviruses and xenoretroviruses 16-18. The general conclusion has been that it is unlikely that the syndrome is caused by a single etiologic agent. The mechanisms mediating CFS are poorly understood, and there are few well designed studies examining its cause. The symptoms of CFS are similar to those experienced during viral infections such as infectious mononucleosis or influenza or in the setting of therapy with cytokines such as interferon or interleukin-2. It has been speculated that some or all the symptoms are reflective of an altered immune response to some pathogen with over production of one or more cytokines. An alternative hypothesis suggests that a number of infectious agents are involved and result in a regulatory imbalance of cytokines and the patient with CFS is unable to reestablish the appropriate balance of cytokines. These theories have been supported by reports of immune deficiency seen associated with CFS19.
Source: Selin LK, Wlodarczyk MF, Kraft AR, Nie S, Kenney LL, Puzone R, Celada F. Heterologous immunity: immunopathology, autoimmunity and protection during viral infections. Autoimmunity. 2011 Jun;44(4):328-47. doi: 10.3109/08916934.2011.523277. Epub 2011 Jan 20. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3633594/ (Full article)