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Impaired function of polymorphonuclear leukocytes exuded into bronchoalveolar spaces infected with Pseudomonas
1First Department of Internal Medicine, Kumamoto University Medical School, Japan.
Abstract:
Steroid-treated and untreated rabbits were infected transbronchially with Pseudomonas aeruginosa. The polymorphonuclear leukocytes (PMN) exuded into the bronchoalveolar spaces were obtained by lavage 18 hr later, superoxide (O2-) production and chemotactic activity were studied. In the steroid-treated group, there was a heightened susceptibility to the infection, as compared to findings in the untreated group. The lung exudate PMN in the steroid-treated group showed a significant decrease (p less than 0.05) in O2- production, and somewhat depressed chemotactic activity. In the untreated group, both O2- production (p less than 0.01) and chemotactic activity (p less than 0.001) of lung exudate PMN doubled, compared with findings in blood PMN. There was, however, no significant difference between lung exudate PMN and blood PMN in the steroid-treated group. Impaired PMN function in the steroid-treated group was also observed in case of casein-induced lung exudate PMN. These results suggest that the antibacterial function of PMN exuded in the infected lung may be impaired in steroid-treated hosts, hence an enhanced susceptibility to lung infection.
Insights
Corticosteroids impair the function of polymorphonuclear leukocytes (PMN), reducing their ability to fight Pseudomonas aeruginosa lung infections. This impairment leads to increased susceptibility to bacterial infections in steroid-treated rabbits.
Area of Science:
- Immunology
- Pulmonary Medicine
- Microbiology
Background:
- Corticosteroids are widely used to suppress inflammation.
- Their impact on immune cell function, particularly in the context of bacterial lung infections, requires further elucidation.
- Pseudomonas aeruginosa is a significant opportunistic pathogen causing severe lung infections.
Purpose of the Study:
- To investigate the effect of steroid treatment on the function of polymorphonuclear leukocytes (PMN) in rabbits infected with Pseudomonas aeruginosa.
- To assess the role of impaired PMN function in steroid-induced susceptibility to lung infections.
Main Methods:
- Rabbits were infected transbronchially with Pseudomonas aeruginosa, with one group receiving steroid treatment.
- Polymorphonuclear leukocytes (PMN) were isolated from bronchoalveolar lavage fluid 18 hours post-infection.
- Superoxide (O2-) production and chemotactic activity of PMN were measured.
- PMN function was also assessed in casein-induced lung exudates.
Main Results:
- Steroid-treated rabbits exhibited heightened susceptibility to Pseudomonas aeruginosa infection.
- Lung exudate PMN from steroid-treated rabbits showed significantly decreased superoxide production and depressed chemotactic activity compared to untreated rabbits.
- In untreated rabbits, lung exudate PMN displayed doubled superoxide production and chemotactic activity compared to blood PMN.
- PMN function was impaired in steroid-treated rabbits, both in response to bacterial infection and casein challenge.
Conclusions:
- Steroid treatment impairs the antibacterial function of polymorphonuclear leukocytes (PMN) in the lung.
- This impairment of PMN function contributes to enhanced susceptibility to Pseudomonas aeruginosa lung infections in steroid-treated hosts.
- The findings highlight a critical mechanism by which corticosteroids can compromise host defense against bacterial pathogens.