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Bronchoalveolar Lavage of Murine Lungs to Analyze Inflammatory Cell Infiltration
Published on: May 4, 2017
Functional age-dependent changes in bronchoalveolar lavage rat cells
1Escuela de Ciencia y Tecnologia, Universidad Nacional de General San Martin, Buenos Aires, Argentina. agoldman@unsam.edu.ar
Insights
Alveolar macrophages (AMs) in young rats show reduced adherence, phagocytosis, and TNF-alpha secretion. These functional differences in AMs may explain why young children are more susceptible to lung infections.
Area of Science:
- Immunology
- Respiratory Medicine
- Developmental Biology
Background:
- Alveolar macrophages (AMs) are crucial for lung defense against inhaled pathogens.
- Young children exhibit higher susceptibility to respiratory infections, suggesting developmental factors influence immune responses.
Purpose of the Study:
- To investigate the functional development of AMs in a rat model.
- To correlate AM functional capacity with age-related changes in immune defense.
Main Methods:
- Assessed AM adherence, chemotaxis, and phagocytosis in young, intermediate, and adult rats.
- Measured TNF-alpha secretion and two cytotoxic mechanisms: antibody-dependent cellular cytotoxicity (ADCC) and immune complex-triggered cytotoxicity (ICC).
Main Results:
- Young rats had lower AM adherence and phagocytosis.
- Chemotaxis varied with age, peaking in intermediate rats.
- TNF-alpha production was undetectable in young rats.
- ICC decreased with age, while ADCC increased.
Conclusions:
- Developmental stage significantly impacts AM function.
- Immature AMs exhibit impaired antimicrobial functions, potentially explaining increased lung infection susceptibility in the young.
Abstract:
Alveolar macrophages (AM) are located at the first line of non-specific defense against inhaled antigens in the lower respiratory tract and therefore represent the major effector cell in antimicrobial defense. Since children under 2 years are known to manifest increased susceptibility to lung infections we used a rat model to study functional capacities of the AM during different stages of development We analyzed several steps of the phagocytic process (adherence, chemotaxis and ingestion) as well as two different mechanisms of cytotoxicity [antibody dependent cellular cytotoxicity (ADCC) and cytotoxicity triggered by immune complex (ICC)] and tumor necrosis factor (TNF-alpha) secretion. We used young (4-6 weeks old), intermediate (16-25 weeks old) and adult (36-45 weeks old) rats. Adherence and phagocytic capacities of AM were lower in young rats compared to intermediate and adult animals. Chemotaxis towards the C5a complement component was low in the first two months of life, then it increased in the intermediate group and fell again in adults. Bronchoalveolar lavage (BAL) cells from young rats did not produce detectable TNF-alpha levels even when stimulated with phorbol 12-myristate 13-acetate (PMA). When we studied two different cytotoxic mechanisms we found that ICC markedly declines from youth to adulthood while ADCC showed a steady increase from youth to adulthood. In conclusion, our data show differences that may help to explain in part the enhanced susceptibility to pulmonary infections found in young children.