Finally, to account for reduced Ltb-deficient ALL growth in vivo, we measured changes in Il7 expression in mice transplanted with 3×106Ltb+/+ ALLs, 3×106Ltb-/- ALLs, and 9×106Ltb-/- ALLs (3×Ltb-/-). The gene discussed is IL7; the disease is acute lymphoblastic leukemia.