A canine lymphocyte surface antigen detectable by a monoclonal antibody (DT200).

A murine monoclonal antibody (DT200) was raised against a 210,000-dalton (210 K) lymphocyte surface protein (a member of the lymphocyte antigen known as T200) which was purified from a canine lymphoid tumor by preparative slab gel electrophoresis. In immunoblotting studies of electrophoretically separated plasma membranes from five cases of canine lymphoma, the antibody detected two antigenically intact peptides at 95 and 110 K which, based on previous polyclonal anti-210 K antiserum immunoblotting and peptide mapping studies, may represent the protease-resistant fragment of the canine T200 molecule. Since DT200 retains its reactivity in formalin-fixed, paraffin-embedded tissue sections, 13 dogs with malignant lymphoma and a panel of normal lymphoid and nonlymphoid tissues were studied using an indirect immunoperoxidase technique. The antigen was localized predominantly to the surface membrane of lymphoid cells. DT200 reacted strongly with all five histological subtypes of lymphoma tested while moderate reactivity was detected in normal B and T cell areas of lymph node, spleen and tonsil. Thymocytes and selected hemopoietic precursors were weakly reactive with DT200 while plasma cells, mature granulocytes, red cells and megakaryocytes were unstained. It was concluded that DT200 is a useful reagent for the diagnosis of malignant lymphoma particularly in extranodal sites and may prove valuable in the investigation of the structure and function of T200 in the dog.