Immunoperoxidase labeling of DLBCL cell lines using the JC12 monoclonal antibody. The GCB-derived cell lines SUDHL6 and SUDHL10 are FOXP1 negative by immunohistochemistry, while the GCB-derived cell line DB, the ABC-like DLBCL cell lines OCI-Ly3 and OCI-Ly10, and the unsubtyped DLBCL cell line HLY-1 exhibit strong nuclear positivity. Cells were counterstained with hematoxylin Gill No. 2 (Sigma-Aldrich, St Louis, MO), mounted in Aquatex (VWR International, Poole, United Kingdom) and viewed using a bright field microscope (Axioskop; Zeiss, Welwyn Garden City, United Kingdom) fitted with a 40×/0.65 numerical aperture objective (Zeiss). The images were captured using a Micropublisher 5MP RTV camera (QImaging, Surrey, BC).