(a) Immunostaining of p-gp in a freshly isolated rat brain capillary (primary Ab: MAB C219; secondary Ab: FITC-conjugated rabbit anti-mouse IgG). (b) P-gp detection by Western blot using the MAB C219. Left lane: brain capillaries; right lane: p-gp overexpressing cell line (MDR+)P388 as positive control. (c) Immunostaining of coronar sections of the brains of nude mice, using the polyclonal AB-1 Ab. Healthy animal, with P-gp expression in capillaries and larger blood vessels in the cerebrum (bottom) and the submeningeal arteries and veins (top). (d) Intracerebral human glioblastoma (U-87 MG) with immunopositive capillary endothelia and negative tumor cells. The arrow points to the ependyma.