Poly-ICLC enhances the T-cell expression of α4-integrin (CD49d), which confers efficient CNS-tumor homing of Ag-specific T-cells. (A and B), C57BL/6 mice bearing day 10 i.c. M05 tumors received 5 × 10 6 naive OT-1 mouse-derived T-cells, then OVA-vaccines and/or poly-ICLC administrations on days 10 and 15. BILs (A) and SPCs (B) were harvested on day 16, and evaluated for the α4-integrin expression on CD8+, OVA-tetramer+ cells by flow cytometry. (A), numbers represent the percentage of α4-integrin+/CD8+ (upper panel), α4-integrin+/OVA+ cells (lower panel) in lymphocyte-gated BIL populations. (B), numbers represent the percentage of α4-integrin+/OVA+ cells in lymphocyte-gated SPC populations. (C), C57BL/6 mice bearing day 15 i.c. GL261 tumors received 5 × 10 6 naive Pmel-1 mouse-derived T cells, then hgp100-vaccines and/or poly-ICLC administrations on days 15 and 20. BILs were harvested on day 21, and evaluated for the α4-integrin expression on CD8+/TCRvβ13+ cells by flow cytometry. Numbers represent the percentage of α4-integrin+/TCRvβ13+ T-cells in lymphocyte-gated populations. (D and E), mAb-mediated blockade of α4-integrin inhibited the CNS-tumor infiltration of OVA-specific T-cells, while not depleting Ag-reactive T-cells systemically. C57BL/6 mice bearing day 10 i.c. M05 tumors received i.p. injections of anti-α 4-integrin mAbs (R1-2, 150 μg/mouse and 9C10, 150 μg/mouse), or control isotype mAb (rat IgG2bK, clone, A95-1, 300 μg/mouse) at 2 hrs before i.v. adoptive transfer of 5 × 106 naïve OT-1 mouse-derived T-cells and subsequent OVA-vaccination and poly-ICLC administration. On day 13, the mice received the 2nd OVA-vaccination and poly-ICLC administration at 2 hrs following the 2nd i.p. mAb injections. BILs, SPC and lymphocytes from draining inguinal (i)LNs were harvested on day 16. Numbers of CD3+/OVA tetramer+ BILs per mouse (D), and the presence of CD8+, OVA-tetramer reactive T cells in iLN and SPC are depicted (E). Data are representative of 3 independent experiments with similar results.