To evaluate the effects of TSLP on CRLF2 B-ALL cell survival in vitro, we treated the human CRLF2 B-ALL cell lines Mutz-5 (established from a relapsed 26-year-old patient) and MHH-Call-4 (hereafter referred to as Call-4) (established from 10-year-old patient at diagnosis) with increasing concentrations of TSLP (0–15,000 pg/mL) for 9 days. This evidence concerns the gene TSLP and acute lymphoblastic leukemia.