TNFSF13B and graft versus host disease: Apart from infiltration accommodation, B cell response, including the interaction between follicular Th cells and germinal center B cells, as well as the ratio of B-cell activating factor of the TNF family (BAFF) to B cells, also impacts from the umbilical cord (UC)-MSC-EVs treatment, resulting in improvement of Scl-GVHD model [40].