CD19 and cancer: IL10‐producing CD19+CD27+ memory B cells, CD19+CCD24hiCD27+ B10 cells,3, 4, 5, 6 and CD19+CD24hiCD27int plasmablasts,7 IL10‐and PDL1‐expressing CD19+CD24hiCD38hi immature B cells,8, 9, 10 IL10‐ and IgG4‐generating CD19+CD25hiCD71hi BR1 cells,11 granzyme B‐producing CD19+CD38+CD1d+ IgM+CD147+ GrB+12 and CD5+D43+CD86+CD147+ Breg cells,13 adenosine‐forming CD39+CD73+ B cells14 and TGF‐ and IDO‐producing induced Breg cells15 regulate and suppress T, B, NK, and dendritic cell responses during infection, autoimmunity, cancer, allergy, and pregnancy in mice and humans.