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In situ separation of bacterial trapping and killing functions of the perfused liver
Abstract:
CF-1 mice cleared and killed 80% of a 1.2 x 10(9) intravenous dose of Salmonella typhimurium after 30 min. The perfused mouse liver trapped 70% of a similar dose of S. typhimurium in a single pass, but in the perfusion model no significant killing of the trapped organisms was observed. The perfused rat liver also avidly trapped bacteria. Because of its larger size, we have been able to devise techniques to experimentally distinguish between the bacterial trapping and killing functions of this organ. When the liver was washed free of blood with sterile M-199, over 70 to 80% of a 10(6) to 10(10) dose of viable S. typhimurium was trapped after a single pass, but no significant bacterial killing was observed. When blood or plasma was added to the perfusion medium, over 50% of the trapped bacteria were killed in 15 to 30 min. Phase contrast and electron micrographs of perfused livers showed extensive extracellular trapping of bacteria in the sinusoids. Our data show that humoral factors are apparently not necessary for efficient trapping of live Salmonella by the perfused rat liver but are an absolute requirement for bacterial activity of the organ.
Insights
The liver efficiently traps Salmonella bacteria, but requires blood or plasma factors to kill them. This study distinguishes the liver
Area of Science:
- Immunology
- Hepatology
- Microbiology
Background:
- The liver plays a crucial role in clearing pathogens from the bloodstream.
- Understanding the liver's mechanisms for bacterial clearance is vital for treating infections.
Purpose of the Study:
- To differentiate the bacterial trapping and killing functions of the liver.
- To investigate the role of humoral factors in liver-mediated bacterial clearance.
Main Methods:
- Utilizing a perfused rat liver model to study Salmonella typhimurium clearance.
- Comparing bacterial trapping and killing in the absence and presence of blood/plasma.
- Employing phase contrast and electron microscopy to visualize bacterial localization.
Main Results:
- The perfused rat liver efficiently trapped 70-80% of Salmonella typhimurium in a single pass.
- Bacterial killing was negligible in a blood-free perfusion medium.
- Addition of blood or plasma significantly enhanced bacterial killing (over 50% in 15-30 min).
- Extensive extracellular trapping of bacteria within liver sinusoids was observed.
Conclusions:
- The liver possesses a potent intrinsic capacity for trapping circulating bacteria.
- Humoral factors present in blood or plasma are essential for the bactericidal activity of the liver.
- This study delineates distinct roles for trapping and killing in hepatic bacterial clearance.