This paper is hard core science and too methodological for you to bother reading but, I report it to show how complex the B cells are. We usually define B memory cells by a marker called CD27. If B cells express CD20+/CD19+ and CD27. They are called memory B cells. In this paper they look at the expression of a number of markers and they see a lot of diversity. They define classical memory B cells by the co-expression of CD21 and CD27. CD21 is a receptor that EBV uses to express B cells. This study suggests that by adding more markers into the detection you can see it is alotmore complicated. So the question is which ones are important in MS?
Ioannidis LJ, Mitchell AJ, Zheng T, Hansen DS. CyTOF mass cytometry analysis of human memory CD4+ T cells and memory B cells. STAR Protoc. 2022 Mar 30;3(2):101269.
High-dimensional mass cytometry provides unparalleled insight into the cellular composition of the immune system. Here, we describe a mass-cytometry-based protocol to examine memory CD4+ T cell and memory B cell (MBC) responses in human peripheral blood. This approach allows for the identification of >50 distinct memory CD4+ T cell and MBC populations from a single clinical sample. This highly reproducible protocol has been successfully applied to multiple infectious disease settings to identify correlates of susceptibility or protection from infection. For complete details on the use and execution of this protocol, please refer to Ioannidis et al. (2021).