Tumor infiltration with T cells in the absence of tolerogenic APCs. (A) C57BL/6 SCID mice were adoptively transferred intravenously with 1 × 106 naive anti-HA CD4+ T cells. One day later, they were challenged with 1 × 106 A20HA given intravenously. Twenty-one days after tumor challenge, mice were humanely killed, and histologic sections of their spleens were stained with anti-B220 antibody (violet) to identify tumor cells and with anti-CD3-ϵ (brown) to identify T cells by immunohistochemistry. Slides were then counterstained with hematoxylin (blue). Close contact between tumor cells and T cells is revealed (inset). (B) BALB/c SCID (left) or C57BL/6 SCID (right) mice were challenged with 1 × 106 A20HA intravenously on day 0. Fourteen days later, tumor-bearing mice were adoptively transferred with 1 × 106 anti-HA-specific CD4+ T cells. One week later, mice were humanely killed, and their livers were removed. Serial histologic sections were performed and stained as detailed.
