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Production of a neutrophil chemotactic factor by endotoxin stimulated alveolar macrophages in vitro
Abstract:
Alveolar macrophages (AM) isolated from normal guinea-pigs and from those chronically exposed to endotoxin (LPS) were cultured in the presence of various concentrations of LPS (from 0.5 ng to 5 micrograms/ml). The presence of a neutrophil chemotactic factor (NCF) in culture supernatants was tested in migrations chambers. Contamination of all reagents has been tested using LAL test (Limulus Amoebocyte Lysate). The results indicate a production of NCF with low LPS concentrations (0.5 and 5 ng/ml) within the first 6 h of incubation: when larger doses are used the response decreases and a significant inhibition is observed with 5 micrograms LPS/ml (P less than or equal to 0.05). When contaminated medium was used, all responses observed were three times higher than with LPS-free medium (P less than or equal to 0.01). However, the response pattern was the same. AM from chronically exposed animals exhibit the same response patterns: the magnitude of NCF production was higher than with normal AM but not significantly. The data suggests that initial conditions of AM in vitro or in vivo with reference to LPS contamination have to be determined as they are of importance when AM NCF production has to be tested.
Insights
Alveolar macrophages (AM) produce neutrophil chemotactic factor (NCF) in response to low endotoxin (LPS) levels. However, high LPS concentrations inhibit NCF production, and reagent contamination significantly impacts results.
Area of Science:
- Immunology
- Cell Biology
Background:
- Alveolar macrophages (AM) play a crucial role in lung immunity.
- Endotoxin (lipopolysaccharide, LPS) is a potent immune stimulator.
Purpose of the Study:
- To investigate the effect of varying LPS concentrations on NCF production by AM.
- To assess the influence of chronic LPS exposure and reagent contamination on AM function.
Main Methods:
- Primary AM cultures from normal and chronically LPS-exposed guinea-pigs.
- Incubation with a range of LPS concentrations (0.5 ng/ml to 5 µg/ml).
- Measurement of neutrophil chemotactic factor (NCF) in culture supernatants using migration chambers; Limulus Amoebocyte Lysate (LAL) test for reagent contamination.
Main Results:
- AM produced NCF at low LPS concentrations (0.5-5 ng/ml) within 6 hours.
- Higher LPS doses (≥5 µg/ml) significantly inhibited NCF production (P ≤ 0.05).
- LPS-free medium showed significantly lower responses compared to contaminated medium (P ≤ 0.01), though response patterns remained consistent. Chronically exposed AM showed higher NCF production, but not significantly.
Conclusions:
- AM NCF production is dose-dependent on LPS, with low concentrations stimulating and high concentrations inhibiting.
- Reagent contamination and prior in vivo LPS exposure significantly influence AM responses in vitro.
- Careful determination of initial conditions is essential for accurate assessment of AM NCF production.