Siglec-10⁺ lymphocytes bind to vessels using VAP-1. (A) Expression of human VAP-1 on mesenteric lymph node vasculature of KOTG mice (left) detected by FITC-Jg-2.10 antibody. A high endothelial venule is pointed out by a white arrow. Lack of expression shown in KO mice (right). Staining with a negative control antibody is shown in the inset. Scale bar represents 50 μm. (B) Purity of the B cells and their Siglec-10 expression used for ex vivo binding assays. Fluorescence-activated cell sorter histograms of CD19 and Siglec-10 expression are shown. Negative control (neg co) antibody was polyclonal anti–P-selectin antibody. (C) Ex vivo frozen section binding assays were used to analyze lymphocyte binding to vessels in mesenteric lymph nodes obtained from VAP-1 KO and VAP-1 KOTG mice. The function of Siglec-10 was blocked by incubating the cells before the assay with anti–Siglec-10 antibody. The results are shown as percentage of control binding (number of KOTG vessel-bound lymphocytes incubated with a nonblocking control mAb is defined as 100%; mean ± SEM). ***P < .001.