GFP⁺-,

neo⁺-transduced CTLs infiltrate target tissues. Representative histologic sections showing patterns of CTL localization in dogs receiving neo-transduced, donor-derived, recipient-specific CTLs and DLA-haploidentical marrow (A-D) compared to autologous CTLs and marrow (E-G).Neo⁺ CTLs localized to sites common to GVHD but only in dogs receiving allogeneic marrow. Aggregates ofneo⁺ cells were present in areas adjacent to the portal tracts identified by the hepatic portal vein (PV) (A) and splenic periarteriolar lymphatic sheaths (PALS, arrow) (B). Increased numbers of neo⁺ cells were also present within the lamina propria of the colon (arrows) (C) and scattered throughout the pulmonary interstitium (D). Autologous CTL infusions (E-G) resulted in random distribution of gene-marked T cells in liver (E), colon (F) (arrow indicates examples of neo⁺cells), and spleen (G). A full description of ISH-PCR assay and tissue controls (H-J), as described in “Materials and methods” and elsewhere,26 27 was used to validate these findings. Bar, 100 μm; original magnification × 100 (A, C, E, F, H, J) and × 40 (B, D, G, I).