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Immunology of pyelonephritis in the primate model: live versus heat-killed bacteria
Abstract:
We produced nonobstructive pyelonephritis in the rhesus monkey (Macaca mulatta) by means of a retrograde inoculation of Escherichia coli to the point of pyelotubular backflow. To evaluate the immune response separate from the effects of infection, we introduced heat-killed bacteria in the same fashion. The disease from live bacteria is self-limited and associated with both a local and generalized immune response. The most marked cellular response is in the regional lymph nodes and is more specific to the bacterial antigen than is generalized stimulation of the immune system. Dead bacteria, while eliciting the formation of serum antibody to the O antigen, appear to ablate the cellular response seen with live bacteria. Loss of renal tubules with attended scarring and loss of renal function does occur from live bacteria. This does not appear to be due to the antigen alone (unless a heat labile antigen is responsible), because heat-killed bacteria do not cause renal scarring. Thus, renal damage seems dependent on an active infection and not on the immune response.
Insights
Active infection with Escherichia coli causes kidney damage (pyelonephritis) in rhesus monkeys, not the immune response alone. Live bacteria trigger a specific immune response, while dead bacteria do not cause scarring.
Area of Science:
- Nephrology
- Immunology
- Microbiology
Background:
- Pyelonephritis, a kidney infection, can lead to renal scarring and function loss.
- Understanding the interplay between infection and immune response is crucial for treatment strategies.
Purpose of the Study:
- To investigate the role of active infection versus immune response in causing renal damage during pyelonephritis.
- To differentiate the effects of live and heat-killed Escherichia coli on the immune system and kidney pathology.
Main Methods:
- Nonobstructive pyelonephritis was induced in rhesus monkeys via retrograde inoculation of Escherichia coli.
- Heat-killed bacteria were used to isolate the immune response from active infection effects.
- Immune responses (cellular and humoral) and renal pathology were assessed.
Main Results:
- Live Escherichia coli infection led to a self-limited disease with local and generalized immune responses, primarily in regional lymph nodes.
- Heat-killed bacteria elicited serum antibody production but suppressed the cellular immune response seen with live bacteria.
- Renal tubule loss and scarring, indicative of kidney damage, were observed with live bacteria but not with heat-killed bacteria.
Conclusions:
- Renal damage in this model of pyelonephritis is dependent on active bacterial infection, not solely on the immune response to bacterial antigens.
- The immune response to Escherichia coli involves specific cellular components that are distinct from generalized immune stimulation.
- Heat-labile antigens may play a role in the pathogenesis of renal scarring, but active infection is the primary driver of damage.