The PAX-5 gene is essential for B-cell differentiation. There are at least four isoforms, of which PAX-5a has been most studied. PAX-5 encodes the 50 kDa B-cell specific activator protein, BSAP. PAX-5 is expressed by pro-, pre-and mature B-cells, but is downregulated during terminal differentiation of plasma cells. PAX-5 influences the expression of other B-cell specific genes, including CD19 and CD20 and CD79a, preceding the expression of CD20. PAX-5 is silenced at the plasma cell stage under the influence of B-lymphocyte-induced maturation protein-1 (PRDM1). PAX-5 is expressed during mouse embryogenesis within the developing brain in a way that is temporarily and spatially tightly condoled. PAX-5 deficient mice show deformation of the mid-brain. Expression in human embryogenesis occurs in the mesoencephalon and spinal cord. Pretreatment: Heat induced epitope retrieval in 10 mM citrate buffer, pH6.0, for 20 minutes is required for IHC staining on formalin-fixed, paraffin embedded tissue sections. (dilution 1:100 - 1:200) The optimal dilution for a specific application should be determined by the investigator. Note: Dilution of the antibody in 10% normal goat serum followed by a goat anti-mouse secondary antibody-based detection is recommended. Control tissue Tonsil; staining nuclear