Ki-M6 immunostaining in routinely processed sections of reactive and neoplastic human lymphoid tissue

A. Gloghini, R. Volpe, A. Carbone

Research output: Contribution to journalArticlepeer-review


A monoclonal antibody, termed Ki-M6 (CD68), which shows a restricted reactivity to cells of the monocyte/macrophage system. Has been evaluated primarily with the use of cryostat sections. In this study the authors could assess that the Ki-M6 antibody recognizes a fixation-resistant epitope in most human macrophages. The Ki-M6 immunoreactivity with monocyte/macrophage-related cells was established by testing on routinely processed samples of reactive and neoplastic lymphoid tissues; it was compared with the staining for vimentin (V9) and S-100 protein antibodies, with visualization of the stationary elements of lymphoid tissues, with the aim of establ8ishing its value in the study of the nonlymphoid microenvironment. The Ki-M6 antibody reactivity could be achieved with Bouin-fixed, paraffin-embedded tissue sections, without any proteolytic treatment, with the use of the avidin-biotin complex (ABC) method, especially after overnight incubation time at 4°C. Some reduction in antigenic reactivity was observed in B5- or formaldehyde-fixed samples. The antibody reacted with macrophages of all different lymph node compartments; a broad reactivity against cells of macrophage lineage, including multinucleated giant cells, was observed in epithelioid granulomas. Ki-M6-positive cells other than classic macrophages were the so-called 'plasmacytoid T-cells' and cells displaying elongated cytoplasms with fibroblastic-like features. Granulocytes, follicular dendritic reticulum cells, and interdigitating reticulum cells did not reveal any reactivity with Ki-M6 antibody. In malignant lesions, neoplastic cells of follicular and diffuse B- and T-cell lymphomas, including large cell non-Hodgkin's lymphomas, and Reed-Sternberg cells of Hodgkin's disease were negative in all cases studied. This study shows that Ki-M6 seems to be another anti-macrophage-specific antibody that reacts, in routinely processed tissue sections, with tissue macrophages but not with accessory cells. Thus, it may be a valuable addition to vimentin and S-100 protein antibodies for investigation of the microenvironmental organization of lymphoid tissues both in normal and neoplastic conditions.

Original languageEnglish
Pages (from-to)734-741
Number of pages8
JournalAmerican Journal of Clinical Pathology
Issue number6
Publication statusPublished - 1990


  • CD68
  • Immunohistochemistry
  • Ki-M6
  • Lymphoid tissue
  • Malignant lymphomas
  • Monoclonal antibodies
  • Monocyte/macrophage

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


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