Our study revealed an increase of two regulatory B cell (Breg) subsets, CD19+B220+CD5+CD1d+ (p <0.0001) and CD19-B220+CD5+CD1d- (p <0.0001), both of which highly overexpress IgM/IgD, PD-L1, and IL-10, in the livers of mice with MASLD and HCC. Here, CD19 is linked to metabolic dysfunction-associated steatotic liver disease.