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Published on: January 21, 2019
Ki-M6 immunostaining in routinely processed sections of reactive and neoplastic human lymphoid tissue
A Gloghini1, R Volpe, A Carbone
1Division of Pathology, Centro di Riferimento Oncologico, Aviano, Italy.
Insights
The Ki-M6 (CD68) monoclonal antibody effectively identifies human macrophages in routinely processed tissue sections. This anti-macrophage antibody shows promise for studying lymphoid tissues in both normal and diseased states.
Area of Science:
- Immunohistochemistry
- Cell Biology
- Pathology
Background:
- Monocyte/macrophage system characterization is crucial for understanding immune responses and tissue microenvironments.
- Availability of specific antibodies aids in precise cell identification and tissue analysis.
- Evaluating new markers like Ki-M6 (CD68) is essential for advancing diagnostic and research capabilities.
Purpose of the Study:
- To evaluate the reactivity of the Ki-M6 (CD68) monoclonal antibody in routinely processed human tissue sections.
- To determine the utility of Ki-M6 in identifying macrophages within lymphoid tissues.
- To compare Ki-M6 performance with established markers like vimentin (V9) and S-100 protein.
Main Methods:
- Immunohistochemical staining using the avidin-biotin complex (ABC) method on Bouin-fixed, paraffin-embedded tissue sections.
- Testing on reactive and neoplastic lymphoid tissues, including lymph nodes and granulomas.
- Comparative analysis with vimentin (V9) and S-100 protein staining.
Main Results:
- Ki-M6 antibody recognizes a fixation-resistant epitope in most human macrophages.
- Strong reactivity observed in macrophages across lymph node compartments and in epithelioid granulomas.
- Ki-M6 showed no reactivity with granulocytes, dendritic cells, or neoplastic cells of B- and T-cell lymphomas and Hodgkin's disease.
Conclusions:
- Ki-M6 is a valuable anti-macrophage antibody suitable for routinely processed tissue sections.
- It demonstrates specific reactivity with tissue macrophages, excluding accessory cells and lymphoid malignancies.
- Ki-M6 serves as a useful tool, alongside vimentin and S-100, for investigating lymphoid tissue microenvironments.
Abstract:
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 establishing 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 degrees 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.
