Figure 1.

Histopathology and immunohistochemistry for LMP1 in lymphoma and lymphoid infiltrate. (A) Follicular center cell lymphoma (lineage 3), large cell type. The normal architecture of the spleen is effaced by sheets of large neoplastic cells with abundant cytoplasm. The nuclei are irregularly shaped, with clumped or marginated chromatin and sometimes prominent nucleoli. Mitotic figures are frequently present. (Hematoxylin and eosin; ×600.) (B) Lymphoid infiltrate in the lung. An aggressive lymphoid-cell infiltrate (lineage 6) has invaded the adjacent alveolar tissue. Analysis of DNA extracted from this tissue demonstrated monoclonal heavy chain rearrangement on Southern blot. A high level of LMP1 was detected by immunoblot analysis of a protein lysate prepared from this tissue. (Hematoxylin and eosin; ×200.) (C) Expression of LMP1 in the lymphoid infiltrate shown in B. The tissue was stained with rabbit polyclonal anti-LMP1 and detected with an immunoperoxidase-tagged goat anti-rabbit serum. LMP1 is detected as dark brown staining in the cell membrane, with some cells showing the characteristic capping. (×1,000.) (D and E) Expression of LMP1 in lymphoma tissue and negative-staining control (lineage 3). The splenic lymphoma tissue was stained with either rabbit polyclonal anti-LMP1 (D) or normal rabbit serum at same dilution (E). The staining was detected with fluorescein-conjugated goat anti-rabbit antibody. LMP1 is detected as green fluorescence in the plasma membrane, with some cells showing the characteristic capping. (×1,000.) (F) Presence of cytoplasmic Ig in the lymphoma. The same lymphoma tissue depicted in D and E was stained with tetramethylrhodamine B isothiocyanate -conjugated goat anti-mouse IgG. IgG is detected as red fluorescence in the cytoplasm of most cells. This lymphoma also expresses a high level of LMP1 and was shown to be monoclonal by IgH gene rearrangement (see also Fig. 4 A and B). (×1,000.)