Analysis of spleen BMP4 expression at the mRNA and protein levels. (A) Quantification of spleen BMP4 mRNA by quantitative reverse-transcribed polymerase chain reaction, normalized to S14 mRNA. *P < .001 compared with control mice. Errors bars represent SEM. (B-D) Immunochemistry. (B-C) Spleens were isolated, fixed in 10% paraformaldehyde, paraffin-embedded, and cut, and sections were stained with anti-BMP4 antibody (original magnification ×20). (C) Lower magnification of an Epo1 mouse is shown (original magnification ×10). (D) Serial spleen sections from one Z9Epo1 mouse were stained with either anti-BMP4 or anti-F4/80. Pictures are representative of at least 3 independent spleens. BMP4 and F4/80 staining was visualized using an Olympus microscope (original magnification ×20).