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House Dust Endotoxin and Peripheral Leukocyte Counts: Results from Two Large Epidemiologic Studies
Michael B Fessler1, Megan U Carnes2, Päivi M Salo1
1Immunity, Inflammation and Disease Laboratory, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
Exposure to endotoxin in house dust is linked to higher peripheral leukocyte counts, a marker of inflammation. This study reveals a significant association between endotoxin levels and white blood cell numbers in diverse populations.
Area of Science:
- Environmental Health
- Immunology
- Epidemiology
Background:
- Peripheral leukocyte count serves as a biomarker for inflammation and is linked to all-cause mortality.
- While acute causes of high white blood cell counts are known, chronic environmental factors influencing leukocyte numbers are less understood.
Purpose of the Study:
- To investigate the relationship between endotoxin concentration in house dust and peripheral leukocyte counts in humans.
- To explore potential gene-environment interactions in this relationship.
Main Methods:
- Linear regression analysis was used to evaluate the endotoxin-leukocyte relationship in two large cohorts: NHANES (n=6,254) and ALHS (n=1,708).
- Gene-environment interaction was tested in the ALHS, focusing on Toll-like Receptor 4 (TLR4) and its role in the endotoxin-leukocyte association.
Main Results:
- A statistically significant positive association was found between endotoxin concentration and total leukocyte count in the NHANES cohort.
- Similar positive associations were observed for specific white blood cell types (monocytes, lymphocytes, neutrophils) and replicated in the ALHS.
- Suggestive evidence of a gene-environment interaction was noted in the ALHS related to TLR4 haplotype and endotoxin exposure.
Conclusions:
- This study reports the first association between house dust endotoxin and leukocyte count in a national survey, with findings replicated in a farming population.
- Residential endotoxin exposure may influence peripheral leukocyte counts across various settings.
- The findings highlight a potential environmental determinant of leukocyte numbers and inflammation.
