To determine whether integrin-mediated adhesion promotes T-ALL establishment or progression in vivo, we engrafted primary LN3 T-ALL cells into Icam1-/- mice and Icam1+/- littermate controls and assessed leukemic burden after T-ALL establishment in control mice (1-2% blood chimerism; Fig. 3a). This evidence concerns the gene ICAM1 and acute lymphoblastic leukemia.