CD 43

Advanced Immunochemical, Becton Dickinson (Leu22), Biodesign (BL-E/G3), Biogenesis (MEM59), Biogenesis/Biosource (WR14), Biogenex (MT1), Caltag Laboratories (BL-TP43), Coulter (DFT1), Cymbus Bioscience (DFT1), Dako (DF-T1), Labvision Corp (BRA7G), Novocastra (polyclonal), Pharmingen (HIS17, S7, 1G10), Sanbio/Accurate (BLEG3), Sanbio/Monosan (MEM-59), Serotec (DFT-1, DR-14) and Shandon Lipshaw (DFT1).

MT1 is applicable to formalin-fixed, paraffin-embedded sections, but requires enzyme (trypsin) pretreatment before immunostaining. HIER enhances immunoreactivity.

MT1 (Poppema et al, 1987) and the identical antibody DFT-1 (Flavell et al, 1988) recognize a sialoantigen present on normal T cells, myeloid cells and macrophages. Megakaryocytes are variably positive. Both antibodies belong to the CD 43 cluster. There is evidence that the antibody MT1, originally thought to belong to CD 45 (Poppema et al, 1987), binds to an entirely unrelated molecule (Flavell et al, 1988). Both MT1 and DFT-1 recognize surface antigens (190, 110 and 100 kD).

In a review of several published series, MT1 was shown to immunoreact with 30% low-grade B-cell lymphomas, approximately 90% T-cell lymphomas, 69% B-cell and 97% T-cell lymphoblastic lymphomas and 44% anaplastic large cell lymphomas. However, it should be noted that MT1 highlights myeloid cells and macrophages (Norton & Isaacson, 1989a). Although normal small B lymphocytes are MT1- most low-grade B-cell lymphomas are MT1+. However, hairy cell leukemia, MALT lymphoma and follicle center cell lymphomas are notable exceptions. Therefore MT1 is not useful to distinguish between T- and B-cell lymphocytic lymphoma. Furthermore, although MT1 is a reliable marker of mantle cell lymphoma (MCL), it cannot immunophenotypically distinguish MCL from T- or B-cell lymphoblastic lymphomas (Norton & Isaacson, 1989b). Rarely, MT1 marks plasmacytoma/myeloma. It is more often positive than negative in peripheral T-cell lymphomas.
An investigation of 28 extramedullary myeloid cell tumors using paraffin section immunohistochemistry with a panel of myeloid markers revealed CD 43 to be the only antibody that was positive in 100% of cases irrespective of the differentiation of the myeloid cells (Traweek et al, 1993). Further, staining was always intense and widespread.

CD 43 remains less useful than CD 3 and UCHL1 as a marker of T-cell lymphomas. Nevertheless, in appropriate immunohistochemical panels CD43 does play a role in the identification of low-grade B-cell lymphomas and myeloid disorders. Normal tonsil is useful as a control since paracortical cells are MT1+, whilst follicle center cells are negative. The expression of CD 43 in a large B-cell lymphoma may be an indicator of dedifferentiation from a small cell lymphoma.

•Flavell DJ, Flavell SU, Jones DB, Wright DH 1988. Two new monoclonal antibodies recognising T cells (DF-T1) and B cells (DF-B1) in formalin fixed paraffin embedded tissue sections. Journal of Pathology 155:343A.

•Norton AJ, Isaacson PG 1989a. Lymphoma phenotyping in formalin-fixed and paraffin wax-embedded tissues. I. Range of antibodies and staining patterns. Histopathology 14:437-446.

•Norton AJ, Isaacson PG 1989b. Lymphomas phenotyping in formalin-fixed and paraffin wax-embedded tissues: II. Profiles of reactivity in the various tumour types. Histopathology 14:557-579.

•Poppema S, Hollema H, Visser L, Vos H 1987. Monoclonal antibodies (MT1, MT2, MB1, MB2, MB3) reactive with leukocyte subsets in paraffin-embedded tissue sections. American Journal of Pathology 127:418-429.

•Traweek ST, Arber DA, Rappaport H, Brynes RK 1993. Extramedullary myeloid cell tumors. An immunohistochemical and morphologic study of 28 cases. American Journal of Surgical Pathology 17:1011-1019.

Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.