PAX5 and precursor B-cell acute lymphoblastic leukemia: To elucidate whether TLR signaling is involved in the transition of pre-malignant B cells to B-ALL, we next performed a Mouse Toll-Like Receptor Signaling Pathway PCR Array using precursor B cells isolated from the bone marrow (BM) of Pax5+/− and WT mice kept either under SPF (Specific Pathogen Free) conditions or exposed to natural infection (i.e., housed in the conventional facility) both for 3 or 6 months.