3. ALARMINS, ILC ACTIVATION IN RSV INFECTION AND
WHEEZING/ASTHMA
In response to RSV, other viruses
as well as allergens and other triggers involved in wheezing/asthma
pathogenesis, airway epithelium can directly stimulate ILC2 to release
IL-4, IL-5, and IL-13 through the release of alarmins (figure 2). IL-4
drives Th2 cell differentiation and promotes B cell antibody class
switch to IgE-producing-plasma cells
[31-33]. IL-5 recruits and
enhances survival of eosinophils, major component of the Th2
inflammatory infiltrates [34,35]. IL-13 increases goblet cell mucin
expression and development of
airway
hyperresponsiveness [36].
Thus, the alarmins IL-33, IL-25, TSLP and HMGB1, through ILC2
activation, can play a significant role in
promoting the progression of Th2
type response in infants with RSV bronchiolitis and in increasing the
risk of developing recurrent wheezing/asthma and, possibly,
susceptibility to allergic exacerbation in later life [37].