To determine whether the transformation of preleukemic B cells to full-blown B-ALL is in part due to dysregulated expression of inflammatory cytokines in Pax5+/- mice, we measured concentrations of 7 inflammatory cytokines (IL-2, IL-4, IL-6, IL-10, IL-17a, TNF and IFNγ) in the serum of Pax5+/- mice exposed to an infectious environment which developed B-ALL, exposed Pax5+/- mice without B-ALL, and age-matched control wild-type mice. This evidence concerns the gene IL4 and acute lymphoblastic leukemia.