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MedWire News:
Children who are diagnosed with asthma after suffering severe
respiratory syncytial virus (RSV) bronchiolitis in early life appear to
have lower levels of plasmacytoid dendritic cells (pDC) in peripheral
blood than those who do not develop asthma after RSV bronchiolitis,
research shows.
“A substantial
proportion of children who are hospitalized with RSV bronchiolitis go
on to develop recurrent wheezing and asthma,” explain Mario
Castro (Washington University School of Medicine, St Louis, Missouri,
USA) and team.
But they add:
“The immunologic markers that predict the development of
asthma after a severe RSV infection remain to be elucidated.”
Plasmacytoid dendritic
cells (pDC) play a crucial role in antiviral immunity and promoting T
helper cell type 1 polarization, possibly protecting against
development of allergic disease. The researchers investigated whether,
following severe RSV bronchiolitis, lower levels of pDC would be
detected in children with asthma than in those without the condition.
The team isolated
peripheral blood mononuclear cells (PBMC) from 73 children, aged an
average of 6.6 years, who had suffered from severe RSV bronchiolitis in
the first year of life.
Flow cytometry was used
to detect DC surface-markers on PBMC. Total serum IgE and peripheral
eosinophil count were assessed, and allergy skin tests were also
performed.
In total, 33 (45%) of the
children had been diagnosed with asthma by the age of 6 years.
The researchers found
that children with asthma had a significantly lower average number of
pDC than those without the respiratory disease, at 1020 versus
1952 cells per 10 million PBMC.
Analysis also revealed
that children with asthma had a significantly lower average number of
myeloid dendritic cells, at 3836 per 10 million PBMC, than
those without asthma, at 4768 cells per 10 million PBMC.
However, this difference was no longer significant after accounting for
age, gender, race, skin test reactivity, tobacco smoke exposure, and
daycare attendance, notes the team.
There were no significant
associations between pDC levels and markers of atopy, such as skin test
reactivity, peripheral eosinophilia, and IgE levels.
Castro and team conclude
in the journal Pediatric Allergy and Immunology:
“Among children with physician-diagnosed asthma following
severe RSV bronchiolitis, there appears to be a relative deficiency of
peripheral blood pDC.
“Further studies of pDC
before the development of asthma may provide an indication of a
valuable window of opportunity for future intervention and prevention
of this common disease process.” |
