Antibodies, Monoclonal, Humanized/pharmacology; Drug Resistance, Neoplasm; Fusion Proteins, bcr-abl/physiology; Integrin alpha4/chemistry; Neoplasm, Residual/drug therapy; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma/drug therapy; Animals; Bone Marrow/drug effects; Bone Marrow/metabolism; Bone Marrow/pathology; Cell Adhesion; Child; Flow Cytometry; Humans; Integrases/metabolism; Integrin alpha4/genetics; Integrin alpha4/metabolism; Mice; Mice, Inbred NOD; Mice, Knockout; Mice, SCID; Natalizumab; Neoplasm, Residual/metabolism; Neoplasm, Residual/mortality; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma/metabolism; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma/mortality; RNA, Messenger/genetics; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; Stromal Cells/drug effects; Stromal Cells/metabolism; Stromal Cells/pathology