Emerging research suggests that IL-35-producing regulatory B cells accumulate in patients and mouse models of pancreatic cancer, one of the most lethal cancers, characterized by late diagnosis, high mortality, and morbidity. Identification of IL-35-producing B cells can be challenging due to the heterodimeric nature of IL-35 and diversity of cell surface markers that define regulatory B-cell subsets across spectrum of diseases. In this chapter, we describe the methods for the isolation of splenic and tumor-infiltrating murine regulatory B cells and subsequent detection of IL-35 by RT-qPCR and intracellular staining, as well as detection of circulating IL-35 by ELISA. We also describe methods for the detection of IL-35-producing human B cells by flow cytometry, RT-qPCR, and immunofluorescence in the context of pancreatic cancer. This chapter should facilitate the study of regulatory IL-35+ B cells in cancer, autoimmunity, and inflammation.
Keywords: IL-35; Immunosuppression; Intracellular cytokine staining; Pancreatic cancer; Regulatory B cells.