Monoclonal antibody Ki-B3 detects a formalin resistant antigen on normal and neoplastic B cells.

A new monoclonal antibody Ki-B3 produced by a fusion with leukemic cells of a centroblastic/centrocytic lymphoma (m.l. follicular) is introduced. This antibody predominantly recognizes B cells of follicular mantle and germinal center cells, as well as plasma cells in normal lymphoid tissue. Furthermore, 80% of all low- and high-grade B cell lymphomas are stained, whereas among T cell lymphomas, only four of 15 T lymphoblastic lymphomas were positive to Ki-B3. All peripheral T cell lymphomas showed a negative reaction. Additionally, Ki-B3 detects a small percentage of monocytes and some myelomonocytic leukemias. All epithelial tissues as well as all sarcomas tested were invariably negative. Ki-B3 precipitates a 220 kiloDalton (kD) molecular weight antigen similar to the leukocyte common antigen. Presumably Ki-B3 detects a subtype of the leukocyte common antigen that is predominantly expressed on mature and immature B cells. As the antigen is formalin resistant, Ki-B3 can be used in routine hematology on paraffin sections for the detection and differential diagnosis of B cell lymphomas.