Effects of pulmonary exposure to diesel exhaust particles on extrathoracic CD4 polarization in asthmatic mice.

Although diesel exhaust particles (DEP) exacerbate murine allergic asthma, the mechanisms remain unclarified. This study elucidated the effects of pulmonary exposure to DEP on extrathoracic allergen-induced CD4 polarization using an ex vivo system in asthmatic mice. Mice were divided into 4 groups, and vehicle, DEP, ovalbumin (OVA), or DEP + OVA was intratracheally instilled biweekly 5 times. Twenty-four h after the last intratracheal instillation, the spleen was removed. Mononuclear cells were isolated from the spleen and stimulated in vitro with OVA; thereafter, the number of separated CD4(+) cells was counted. The number of separated CD4(+) cells was significantly greater in the OVA or the DEP + OVA group than in the vehicle group. Furthermore, the number was significantly greater in the DEP + OVA than in the DEP or the OVA group. Taken together, in vivo DEP exposure amplified extrathoracic CD4 polarization in asthmatic subjects.