The differentiation of Breg cells mainly depends on the engagement of BCR and CD40.25, 26 In human B cells, STAT3 and Erk activation induced by TLR controls IL‐10 expression.27 The inhibition of STAT3 blocked IL‐10 expression by CD19+ Tim‐1+ cells, suggesting that using STAT3 inhibitors in tumour patients also retards B10 cell development. Here, CD19 is linked to neoplasm.