Implication of TIGIT+ human memory B cells in immune regulation
Regulatory B cells (Bregs) contribute to immune regulation. However, the mechanisms of action of Bregs remain elusive. Here, we report that T cell immunoreceptor with Ig and ITIM domains (TIGIT) expressed on human memory B cells especially CD19+CD24hiCD27+CD39hiIgD-IgM+CD1c+ B cells is essential for effective immune regulation. Mechanistically, TIGIT on memory B cells controls immune response by directly acting on T cells and by arresting proinflammatory function of dendritic cells, resulting in the suppression of Th1, Th2, Th17, and CXCR5+ICOS+ T cell response while promoting immune regulatory function of T cells. TIGIT+ memory B cells are also superior to other B cells at expressing additional inhibitory molecules, including IL-10, TGFß1, granzyme B, PD-L1, CD39/CD73, and TIM-1. Lack or decrease of TIGIT+ memory B cells is associated with increased donor-specific antibody and TFH response, and decreased Treg response in renal and liver allograft patients. Therefore, TIGIT+ human memory B cells play critical roles in immune regulation. Overall design: We  divided peripheral blood B cells of healthy individuals into six different populations based on the expression levels of surface molecules, including IgD, CD24, CD27, CD38 and CD39 . 100-200K cells from each subsets were used for RNA extaction just right after cell sorting  and equal number of cells were stimulated with CpG-B for 16 hours, washed and extracted RNA. Cells collected from 6 different donors were used for RNA-seq.