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Demonstration of bacterial antigen in macrophages in experimental pyelonephritis
1Department of Pathology, Albert Szent-Györgyi Medical University, Szeged, Hungary.
Abstract:
The immunomorphological characteristics of interstitial macrophages with PAS-positive granules were studied in experimental Escherichia coli pyelonephritis in rats, using an anti-E. coli antibody. Immunohistochemical, immunoelectron microscopical, as well as light- and electron microscopical findings were compared at twelve time points between 2 days and 13 weeks after infection. Macrophages with PAS-positive granules were present in the inflammatory infiltrates from the 7th day. The granules were phagolysosomes, filled predominantly with myelin figures. The myelin figures originated mainly from the constituents of the bacterial wall and reacted with the anti-E. coli antibody even 13 weeks after infection. The storage of bacterial residues with preserved antigenic structures for several weeks after infection indicates disturbed phagolysosomal elimination of the bacterial substances in the PAS-positive macrophages. In the formation of macrophages with PAS-positive granules, lysosomal overloading with large amounts of bacteria and cell debris is assumed, leading to consumption of the lysosomal enzymes, consequent incomplete breakdown and retention of the bacterial residues.
Insights
Interstitial macrophages in rats with Escherichia coli pyelonephritis store bacterial residues for weeks. This indicates impaired phagolysosomal function in these PAS-positive macrophages, hindering bacterial clearance.
Area of Science:
- Immunology
- Pathology
- Microbiology
Background:
- Experimental Escherichia coli pyelonephritis in rats is a model for studying bacterial kidney infections.
- Interstitial macrophages play a crucial role in the host immune response to bacterial pathogens.
Purpose of the Study:
- To investigate the immunomorphological characteristics of interstitial macrophages containing Periodic Acid-Schiff (PAS)-positive granules during experimental Escherichia coli pyelonephritis.
- To determine the fate of bacterial components within these macrophages over time.
Main Methods:
- Utilized immunohistochemistry, immunoelectron microscopy, light microscopy, and electron microscopy.
- Examined tissue samples at twelve time points, from 2 days to 13 weeks post-infection.
- Employed an anti-E. coli antibody to trace bacterial antigens.
Main Results:
- Macrophages with PAS-positive granules appeared by day 7 and persisted.
- These granules contained phagolysosomes filled with myelin figures derived from bacterial cell walls.
- Bacterial residues with intact antigenic structures were retained for up to 13 weeks, reacting with the anti-E. coli antibody.
- This suggests a failure in phagolysosomal elimination of bacterial substances.
Conclusions:
- PAS-positive macrophages in pyelonephritis exhibit disturbed phagolysosomal elimination of bacterial residues.
- Lysosomal overloading with bacteria and debris likely leads to enzyme depletion and incomplete bacterial breakdown.
- This retention of bacterial antigens may prolong the inflammatory process or indicate persistent bacterial presence.