Representative images of immunohistochemical staining of tissues with a monoclonal antibody against the JSRV Env protein. Human lung tumor tissue array samples representing grade 0 staining (A), grade 1 staining (B), grade 2 staining (C), and grade 3 staining (D). High magnification (40x) images of human lung tumors with grade 2 (E) and grade 3 (F) staining. Low (4X) and high (40X) magnification images of human lung tumor tissue array sample stained with an isotype control (G and J) and an unrelated antibody-producing hybridoma (H and K). Lack of immunohistochemical staining of human lung tumor tissue arrays in the presence of JSRV Env antibody plus purified JSU-IgG protein (I and L) or JSU-IgG protein alone (M). Human adenocarcinoma in-situ displaying clusters of JSRV Env positive cells (N). Representative images of human adenocarcinoma in-situ (O) and non-neoplastic human lung tissue (P) with no detectable Env staining. Nasopharyngeal carcinoma tissue array showing no detectable Env staining (Q). Lung tissue from an OPA affected sheep stained with the JSRV Env monoclonal antibody (R).