Link Between Systemic Infection and MS Relapse

Multiple sclerosis (MS) can be described as an autoimmune disease where the immune system erroneously attacks the central nervous system. These immune attacks typically result in the onset of a battery of neurological dysfunctions, which spontaneously recovers as the CNS undergoes plastic changes to restore the function of damaged connectivities.

During the spontaneous recovery phase (or remission phase), systemic infections are known to promote the recurrence of immune attacks in the MS lesion. The recurrence of these attacks are known as MS relapse, which results in the reappearance of neurological dysfunctions associated with MS onset. The link between infection and MS relapse is further supported by previous MRI studies demonstrating that MS patients suffering systemic infections have significantly greater blood flow to the MS lesions.

In the recent MRI studies published in April 15th, 2009 issue of the Journal of Neuroscience, mouse models of multiple sclerosis that were subjected to systemic inflammation demonstrate significantly greater blood flow into their MS lesions. Further immunohistochemical analysis confirms that the observed blood flow into MS lesions are indicative of immune cell infiltration into the MS lesions. Consistent with immune cell infiltration, the blood brain barrier (BBB) at the MS lesions appears to overexpress adhesion molecules that promote immune cell entry into the CNS.

The authors of this paper suggested that a potential therapeutic strategy for MS is to target adhesion molecules that may promote immune cell infiltration across the BBB. Although this approach may be an attractive way to treat MS, one potential downfall is that this is based on the hypothesis that the BBB at the MS lesion is physically intact, and that immune cells must rely on adhesion molecules to cross the BBB. However, it is not known whether the BBB is indeed physically intact, and whether immune cells could infiltrate simply through breaches in the blood brain barrier. Perhaps further morphological analysis of cells that make up the BBB, and further assessment on the physical integrity of the BBB, may be important for developing effective therapeutic strategies to treat MS.

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