Schwarz A, Balint B, Korporal-Kuhnke M, Jarius S, von Engelhardt K, Fürwentsches A, Bussmann C, Ebinger F, Wildemann B, Haas J. B-cell populations discriminate between pediatric- and adult-onset multiple sclerosis. Neurol Neuroimmunol Neuroinflamm. 2016;4(1):e309
The authors are not looking for anything other than B cells and so they don't really focus on the memory B cell, but if you think that this population harbours what drives MS then the data jumps at you.
First thing as you get older and encounter more things the immune system is interested in the number of naive (Mature) B cells drops to be replaced with memory B cells.You have to remember these are percentages so if the naive (mature) cells go up memory cells must go down and vice versa, the best way to do this is to calculate absolute numbers then you can see if there are more or less cells.
However, here they look at the B cell populations in young and adult pwMS and compared to health in the young it is clear that people with MS have more B memory cells in their blood.
In relapse the percentage of memory cells go down.
Is this because they are off into the CNS?.
The memory cells (CD19+, CD27+) make up 66%/75.9% (Paedatric/adult) of B cells in CSF compared to 30.1%/33.2% in the remission blood.
So memory B cells are being recruited to or they are retained with in the CNS in MS.
The data in the CSF may create some complexity as it looks like young and adult memory pool is not quite the same, but we have to remember, it is unlikely that every cell found in CNS is pathogenic, many get drawn in because of the adhesion molecules/chemokines and there may be ectopoic resident cells in CNS contributing to the pool.
So the question is which memory B cell subset is causing the damage? However, is it the memory cell is more important than the type of memory cell, which could support the EBV idea as they will get infected in the unswitched (IgD+) state and this will persist in the switched B (IgD-) cells.