Contrasting immunological effects of two disparate dusts - preliminary observations.
BACKGROUND
Modern lifestyle and urbanization have been associated with a raised risk for atopic diseases whereas early and long-term exposure to a farm environment confers protection against atopic sensitization. Immunomodulatory potential and microbiological characteristics of settled airborne dust from an urban house and a barn were examined.


METHODS
Pulmonary inflammation was induced in mice by repeated intranasal administration of dusts. Monocyte-derived human dendritic cells (moDCs) were exposed to dusts followed by coculture with purified naïve T cells. Cytokine/chemokine mRNA and protein levels were analyzed by real-time polymerase chain reaction, enzyme-linked immunosorbent assay and flow cytometry. The dusts were analyzed by cloning and sequencing of 16S rRNA genes (290 sequences) for DNA, lipids, endotoxin and beta-glucan, by live-dead staining, viable counting, isolation and identification of pure cultures (n = 76).


RESULTS
Repeated exposure to house dust elicited pulmonary eosinophilia in mice whereas exposure to barn dust elicited neutrophilic and lymphocytic airway inflammation. Stimulation of moDCs with urban house dust elicited expression of Th2-promoting OX40L and Jagged-1 costimulatory molecules. Dendritic cells (DCs) exposed to house dust directed naïve T cells towards Th2 responses. Exposure of DCs to barn dust elicited the development of Th1-dominated immune responses. Urban house dust contained bacterial debris almost exclusively of human commensal species (corynebacteria, streptococci) whereas barn dust comprised mainly intact, viable bacteria of high diversity and no commensal species.


CONCLUSIONS
Contact to debris originating from human commensal bacteria in urban house dust elicited a Th2-type response whereas barn dust with high bacterial diversity directed the cells towards a Th1 response.
Alenius
Harri
H
Finnish Institute of Occupational Health, Helsinki, Finland. Harri.Alenius@ttl.fi
Pakarinen
Jaakko
J
Saris
Ossian
O
Andersson
Maria A
MA
Leino
Marina
M
Sirola
Kristiina
K
Majuri
Marja-Leena
ML
Niemela
Jari
J
Matikainen
Sampsa
S
Wolff
Henrik
H
von Hertzen
Leena
L
Makela
Mika
M
Haahtela
Tari
T
Salkinoja-Salonen
Mirja
M
D016902:Air Pollution, Indoor / Q000009:adverse effects* / Q000032:analysis; D000818:Animals; D001419:Bacteria / Q000276:immunology / Q000302:isolation & purification; D003713:Dendritic Cells / Q000276:immunology / Q000382:microbiology; D004391:Dust / Q000032:analysis / Q000276:immunology*; D005260:Female; D006801:Humans; D001239:Inhalation; D051379:Mice; D008807:Mice, Inbred BALB C; D010802:Phylogeny; D011014:Pneumonia / Q000276:immunology* / Q000382:microbiology; D011657:Pulmonary Eosinophilia / Q000276:immunology / Q000382:microbiology; D013601:T-Lymphocytes / Q000276:immunology / Q000382:microbiology; D018417:Th1 Cells / Q000276:immunology* / Q000382:microbiology; D018418:Th2 Cells / Q000276:immunology* / Q000382:microbiology
D004391:Dust