Fig. 5. Abnormal spleen development in Barx1^-/- mice. (A) Relationship of the spleen (Sp) in normal neonatal mice to adjacent stomach (St), duodenum (Du) and a fused pancreas (Pa). (B) Invariant size and location of the Barx1^-/- spleen as a small tissue (marked with a dotted line) attached to the dorsal pancreas, which is separate from the ventral pancreatic bud. (C,D) Histologic elucidation of intimate association between splenic and pancreatic parenchyma by H&E stain (C) and insulin immunostaining of prospective pancreatic islets (D, arrowheads) on consecutive tissue sections. (E) Flow cytometric (left) and immunohistochemical (right) analysis of control (+/?) and Barx1^-/- spleen (Sp), indicating normal hematopoiesis and lymphoid colonization (+/? refers to +/+ or +/-). Ter119, B220 and Gr1 are specific markers of red cells, B lymphocytes and granulocytes, respectively. Control and Barx1^-/- spleen also showed identical flow cytometry profiles for T-cell and monocyte surface markers (data not shown).