Subcutaneously implanted 291 tumors are well vascularized and show a pronounced infiltration with T cells.

<p>Tumor cells were injected subcutaneously into the flanks of C57BL/6 mice. Grown tumors were excised, fixed and analyzed by hematoxylin/eosin (H/E) staining or immunohistology using antibodies against CD3 or NKp46. <b>A–F</b>: The respective magnifications are indicated at the top of each image. Panels A and B show the presence of numerous blood vessels (arrows) throughout the tumors in H/E staining. Panels D, E and F represent serial sections of the same position within a tumor. Various blood vessels are visible in H/E staining and the CD3 staining shows infiltration of the tumor with CD3⁺ cells (dark grey/black staining). Less NKp46⁺ cells could be detected in the respective staining of the same position (dark grey/black staining; one cell is marked by an arrow). Panel C depicts a cluster of NKp46⁺ cells, which was sometimes found at the margins of tumors (margin: upper part of the picture). <b>G</b>: Injection of CXCL10-mucin-GPI tends to increase endogenous NK cell infiltration of subcutaneous tumors. Purified CXCL10-mucin-GPI was injected into established 291 tumors. As controls, either the same or a 500×higher molar quantity of commercially available human CXCL10 (rhCXCL10) were injected. As additional controls, the same volume of identically purified sEGFP-GPI was injected or the tumors were left completely untreated. The animals were sacrificed 4 h after injection and infiltration of the tumors was assessed by FACS analysis. The figure shows the percentage of CD3^- NK1.1⁺ cells among the total lymphocyte count with each symbol representing one individual tumor and horizontal bars the average values. Statistical significance was calculated using the Kruskal-Wallis-test (P = 0.19) followed by Dunńs post test (not significant, N.S.).