Figure 1. 91R mAb is specific for human chemokine receptor CCR9. (A) HEK293 cells stably transfected with hCCR9, mCCR9, hCCR4, hCCR5, hCCR6, hCCR8 (open histograms) or the empty pCIneo vector (filled histograms) were stained with 91R mAb and analyzed by flow cytometry. (B) Human leukemia MOLT-4 and Jurkat cells were stained with anti-human CCR9 mAb 91R and 112509 (open histograms) or isotype-matched control mAbs (filled histograms) and analyzed by flow cytometry. (C) Representative flow cytometry analysis of MOLT-4 staining with different doses (0.1–10 μg/ml) of 91R (filled histograms), 112509 (open histograms), or isotype-matched mAb (gray lines) (n = 5). (D) Flow cytometry analysis of human thymocytes using anti-CD4, -CD8 and –CCR9 91R antibodies. Percentages of positive cells in gates of the CD4/CD8 plot are indicated; hCCR9 expression is shown for each subpopulation. (E) Flow cytometry shows a FS/SS dotplot for total human peripheral blood cells and 91R/anti-CD3 staining in the lymphocyte gate. (F) Representative western blot of membrane-enriched fractions of hCCR9- or pCIneo-transfected HEK293 cells, MOLT-4, and Jurkat cells incubated with 91R; the same membrane was probed with anti-CD71 Ab as loading control (n = 3).