Breg subsets from healthy individuals are present within the CD19⁺CD24^hiCD38^hi, CD19⁺CD24^hiCD27⁺, and IgM memory B-cell (current study) populations and inhibit immune responses in part through IL-10 and direct interactions with the target cells. In healthy individuals, there is a balance between regulatory (including Tregs and Bregs/IL-10–expressing B cells) and the nonregulatory immune compartments such as conventional (conv) B and T cells. The study by Khoder et al suggests that the balance between IL-10⁺ B cells and the nonregulatory cells is disturbed in severe cGVHD, but that it may be reset by treatments such as rituximab. Tconv, conventional T cells; Mo, monocytes.