Suplatast tosilate is an
antiallergic drug that selectively suppresses Th2-cytokine production and inhibits
airway hyperresponsiveness and eosinophilic airway
inflammation. This
drug has been also shown to improve pulmonary function and symptoms in
steroid-dependent
asthma, resulting in a decrease in doses of inhaled
corticosteroid. However, the precise mechanism by which
suplatast tosilate exerts an
antiasthmatic effect in vivo remains to be known. Our previous study showed the polarization of circulating type 1 dendritic cells (DC1)/type 2 dendritic cells (DC2) balance toward DC2 in
asthma, which might be associated with its Th2-dominant immune response. In the present study, we attempted to clarify the effect of
suplatast tosilate on DC1/DC2 balance in
asthma. Using multicolor flow cytometry, we enumerated circulating DC1 and DC2 before and 8 weeks
after treatment with
suplatast tosilate in nine patients with
asthma. Before the treatment, the patients with
asthma had a significant higher percentage of DC2 together with a significant lower ratio of DC1/DC2 compared with normal subjects. Administration of
suplatast tosilate significantly decreased the percentage of DC2, but not that of DC1, resulting in a significant raises of the ratio of DC1/DC2. Concomitantly, intracellular
cytokine analysis showed that the percentage of
IL-4 producing CD4+ T cells was significantly decreased after the treatment. These data suggest that
suplatast tosilate normalizes the polarized DC1/DC2 balance toward DC2 in
asthma, which may also alter its Th2-dominant Th1/Th2 balance toward Th1.