Regulatory B cells, helminths, and multiple sclerosis.

Multiple sclerosis (MS) is an inflammatory demyelinating disease affecting the central nervous system. Autoimmunity appears to play a key role in both susceptibility to MS and development of disease, and pathogenesis has been linked to defects in distinct regulatory cell subsets. B cells are known for their capacity to produce antibodies. Recent advances in B cell biology, however, have demonstrated that regulatory B cells, a functional subset of B cells, contribute to tolerance development. Regulatory B cells were originally described in mouse autoimmunity and inflammation models where they dampen inflammation, but have also been found in several helminth infection models. We recently demonstrated that helminth-infected MS patients show a significantly lower clinical and radiological disease activity. Parasite-driven protection was associated with regulatory T cell induction and secretion of suppressive cytokines such as IL-10 and TGF-β. In addition, helminth infections in MS patients induced regulatory B cell populations producing high levels of IL-10, dampening harmful immune responses through a mechanism mediated, at least in part, by the ICOS-B/RP-1 pathway. More importantly, production of IL-10 by B cells in this study was restricted to helminth-infected individuals exclusively.The first part of this chapter will detail the criteria used in this study for selection of helminth-infected MS patients, MS patients without infection, and patients infected with Trypanosoma cruzi. Methods for isolation of peripheral blood CD19(+) cells and in particular for their stimulation with heat-inactivated Staphylococcus aureus Cowan strain, CDw32L cells, and CD40 antibody will also be described in detail. Finally, we will illustrate the procedures used to analyze phenotypic surface markers on these cells and characterize them in terms of IL-4, IL-6, IL-10, TNF-α, lymphotoxin, and TGF-β secretion.