Ephrin-A1 is expressed on endothelial cells in tonsils. (A) Northern blot analysis of ephrin-A1 mRNA expression in selected cell populations isolated from tonsils. Two CD34⁺ cell isolations from 2 different tonsils are shown. Actin hybridization serves as a loading control. (B) Immunohistochemical analysis of ephrin-A1 expression in tonsils. Vessels, in particular HEVs, are stained (top panel left and right, bottom panel right). Anti-ephrin-A1 antibody from Santa Cruz Biotechnology. Original magnification is × 10 or × 40. (C) Immunohistochemical analysis of ephrin-A1 expression in tonsils. Bright staining is observed to the luminal side of HEV endothelial cells. Anti-ephrin-A1 antibody from Zymed. Original magnification is × 63.