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. Here, CD19 is linked to Allergy.