IL-4 in situ hybridization. (A) In situ hybridization with an antisense riboprobe against IL-4 demonstrates gene expression by CNS lymphoma cells. (B) There was no significant hybridization with a sense riboprobe against IL-4 in a parallel section from the same tumor. (C) Tumor cells and vessels in a breast carcinoma metastatic to brain did not exhibit significant hybridization with an antisense riboprobe against IL-4. Original magnification × 200 for panels A-C. (D) In situ hybridization with an antisense riboprobe against IL-4 reveals increased gene expression in a representative CNS lymphoma tumor vessel. (E) There was no significant hybridization with a sense riboprobe against IL-4 in a parallel section from the same tumor. (F) Vessels in normal brain did not exhibit significant hybridization with an antisense riboprobe against IL-4. Original magnification × 400 for panels D-F.