Two kinds of Innate B cells; B-1 and marginal zone B cells
  • Tae Jin Kim Ph.D
  • SLS Colloquia / 2017. 10. 12. pm 04:00 / Room N104, Bldg110
Abstract

B cell compartment is composed of three major subsets ? follicular B (FOB), marginal zone B (MZB), and B-1 cells. Regulatory B cells are IL-10 secreting B cells and appear to be a part of each three population. B-1 cells are divided into fetal liver origin B-1a cells and adult bone marrow origin B-1b cells. FOB cells constitute a major population of B cells in the adult and produce most of highly antigen-specific memory B cells and plasma cells through the germinal center reaction aided by follicular helper T cells. Since it takes a long time for FOB cells to produce highly specific Abs, two kinds of fast Abs are playing roles in combating infections in the early period of infection, which are produced by B-1a cells and MZB cells.

B-1a cells produce natural Abs, which are basically autoreactive as well as cross-reactive to common pathogens. Natural Abs are apparently constitutively produced as even germ-free mice have natural Abs without any infection. Although natural Abs are helpful for the host, they may be potentially dangerous to the host, triggering autoimmune diseases. Some regulatory mechanisms should be present to restrain the overactivity of B-1a cells. Regulation of B-1a cell migration and role of serosal CD4+ T cells in B-1a cell function will be discussed.

MZ cells are fast-reacting B cells that are localized in splenic MZ enriched in blood flow. MZB cells respond rapidly upon blood-borne infection. We addressed how the useful repertoire of MZB cells are preselected and whether there are defects in this MZB cell selection process in the DBA/1 mice and also in autoimmune disease patients. We observed a MZB cell selection abnormality in the DBA/1 mice that are susceptible to collagen-induced arthritis (CIA). The abnormally autoreactive MZB cells were of activated phenotype and expressed a high level of CD80. By depleting this autoreactive population, we could delay the onset of CIA. We are currently studying the dynamics of MZ B cell population after depletion of MZB cells.