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Recruitment of 99m-technetium- or 111-indium-labelled polymorphonuclear leucocytes in experimentally induced
L Guilloteau1, M Pépin, P Pardon
1Institut National de la Recherche Agronomique, Station de Pathologie de la Reproduction, Nouzilly, France.
Abstract:
The recruitment of polymorphonuclear leucocytes (PMNs) during the development of experimental pyogranulomas induced by Corynebacterium pseudotuberculosis was followed in nine male lambs by scintigraphic examination. Autologous blood PMNs were labelled with 99m-technetium or 111-indium and were re-injected intravenously into infected lambs. The functional properties of the labelled cells were monitored 1) in vitro by measuring their phagocytic and bactericidal activity against C. pseudotuberculosis and their chemotaxis under agarose, and 2) in vivo by following scintigraphically their capacity to accumulate in an inflammatory focus induced by intradermal injection of latex beads coated with Salmonella abortus equi lipopolysaccharide. Following inoculation of corynebacteria into the right ear of lambs, radioactive foci were observed to be localized in the right ear and in the draining lymph nodes during the 4 days following inoculation. Histopathological examination performed 32 h after inoculation confirmed the intense accumulation of PMNs at these sites. With the exception of one animal, which presented visible foci in the neck 14 days postinoculation, no radioactive foci were observed during the later phases of experimental infection, despite the presence of multiple pyogranulomas which were confirmed by bacteriological examination after necropsy of the lambs. Histopathological examination of these lesions revealed layers of fibroblasts, lymphocytes, and macrophages surrounding a necrotic centre. The results of these studies suggest that the contribution of PMNs during the chronic phase of inflammation is considerably reduced in comparison with the acute inflammatory phase of the infectious process.
Insights
Polymorphonuclear leucocytes (PMNs) are crucial in acute inflammation during experimental pyogranulomas. Their contribution significantly decreases during the chronic phase of infection, as shown by scintigraphic studies in lambs.
Area of Science:
- Veterinary Immunology
- Infectious Disease Pathology
- Inflammatory Response Mechanisms
Background:
- Experimental pyogranulomas in lambs are induced by Corynebacterium pseudotuberculosis.
- Understanding the role of polymorphonuclear leucocytes (PMNs) in pyogranuloma development is crucial for infection control.
Purpose of the Study:
- To investigate the recruitment and functional contribution of PMNs during experimental pyogranuloma development in lambs.
- To differentiate the role of PMNs in acute versus chronic inflammatory phases of Corynebacterium pseudotuberculosis infection.
Main Methods:
- Autologous blood PMNs were labeled with 99m-technetium or 111-indium and reinjected into infected lambs.
- In vitro functional assays (phagocytosis, bactericidal activity, chemotaxis) and in vivo scintigraphic imaging were used to track PMN activity.
- Histopathological and bacteriological examinations were performed to correlate PMN localization with lesion development.
Main Results:
- Scintigraphy revealed significant PMN accumulation in the infected ear and draining lymph nodes within 4 days post-inoculation.
- Histopathology at 32 hours confirmed intense PMN infiltration at these acute inflammatory sites.
- Limited radioactive foci were observed in later stages, despite established pyogranulomas, indicating reduced PMN involvement in chronic lesions.
Conclusions:
- PMN recruitment is substantial during the acute inflammatory phase of experimental pyogranulomas induced by C. pseudotuberculosis.
- The functional contribution of PMNs diminishes considerably during the chronic phase of this infectious process.
- Chronic lesions are characterized by a cellular infiltrate of fibroblasts, lymphocytes, and macrophages, with minimal PMN presence.