Although it has been accepted that pulmonary exposure to
diesel exhaust particles (
DEP), representative constituents in
particulate matter of mass median aerodynamic diameter < or 2.5 microm (PM(2.5)), exacerbates murine allergic
asthma, the in vivo effects of
DEP on their cellular events in the context of
allergen-specific Th response have never been examined. The aim of this study is to elucidate whether in vivo repetitive exposure to
DEP combined with
allergen (
ovalbumin) facilitate
allergen-specific Th response in the lung using a simple ex vivo assay system. As a result, repetitive pulmonary exposure to
DEP in vivo, if combined with
allergen, amplifies ex vivo
allergen-specific Th2 response in the lung compared to that to
allergen alone, characterized by high levels of
interleukin (IL)-4 and
IL-5. The result suggests that in asthmatic subjects,
DEP promote Th2-prone milieu in the lung, which additively/synergistically augment
asthma pathophysiology in vivo.