1. Interleukin-9 production
in the lungs of infants with severe respiratory syncytial
virus bronchiolitis (Lancet
2004;363:1031-7)
2. Eosionophil activation and cysteinyl leukotriene
production in infants with
respiratory syncytial virus
bronchiolitis (Clin Exp Allergy 2004;34:555-8)
Several studies have suggested that infants
in whom respiratory syncytial virus (RSV) bronchiolitis
develops will have recurrent wheezing and asthma later
in childhood and shown a link between RSV infection
and asthma. It has been suggested that acute infantile
bronchiolitis associated with RSV may share some pathogenic
features. Complicating the picture is the question of
whether there is a link between RSV infection in infancy
and the development of atopy later in childhood. Although
evidence exists showing that the development of atopy
is more common in children who have had RSV infection
in early childhood, it is unknown whether the RSV infection
leads to the development of atopy or if these children
are "preprogrammed" to develop more severe manifestations
of atopy in response to a viral respiratory infection.
Interleukin 9, a type 2 cytokine has been proposed as
a key cytokine in susceptibility to asthma. McNamara
et al. intended to investigate whether interleukin 9
was produced in the lungs of infants with severe RSV
disease and if found, from which cells it originated.
Interleukin 9 mRNA expression, which persisted over
the course of ventilation, was noted in all infants
with bronchiolitis.
In this article, in term infants with RSV
bronchiolitis, investigators confirmed large amounts
of interleukin 9 mRNA and interleukin 9 protein and
neutrophils seem to be the main source of this type
2 cytokine. It has been suggested that interleukin 9
production by neutrophils may contribute to the pathogenesis
of RSV disease. These findings may be relevant to other
disease processes, including acute asthma exacerbation,
in the lung where neutrophils are the predominant inflammatory
cell type. ECP is a specific marker of eosinophil activation
although leukotrienes can be released from a variety
of cells including mast cells, eosinophils and monocytes.
Dimova-Yaneva et al. made an attempt to test the associati
on between eosinophil activation and cysteinyl leukotriene
production in the upper airway secretions of infants
with RSV bronchiolitis. In the majority of their subjects
with RSV bronchiolitis ECP and LTC4 were detectable
in upper airway secretions and were significantly associated
with each other. In this clinical setting much of the
detected LTC4 within upper airway secretions is likely
to originate from the eosinophil, an observation that
may have implications for clinical management and for
delineation of the underlying mechanisms associated
with this illness. |