Staphylococcal enterotoxin (SE) induces T lymphocyte activation along with nasal allergic
inflammation during
rhinosinusitis, but it is under debate on which types of T helper (Th) cells respond exclusively or whether they respond synergically. We hypothesize that their responses may vary based on dose of SE. To test this hypothesis, we initiated to determine the nature of the T cell response and pathological feature upon repeated exposure to
staphylococcal enterotoxin A (SEA) at different doses in the maxillary sinus of rabbits. SEA (0.6 or 60 ng) was instilled daily into the left maxillary sinus of rabbits for 28 days. The right maxillary sinus receiving
normal saline was used as control. Mucosal histological changes were examined by
hematoxylin-
eosin and
toluidine blue staining. Tissue expression of
myeloperoxidase (MPO),
eosinophil cationic protein (ECP), T-box expressed in T cells (T-bet), and GATA
binding protein 3 (GATA-3) were examined using immunohistochemistry. Mucosal levels of representative pro-inflammatory
cytokines were measured using ELISA. SEA at 60 ng/day induced acute
rhinosinusitis, as confirmed by CT scan. Histopathologic examination revealed epithelial disruption, subepithelial
edema, and inflammatory cell infiltration. MPO and T-bet expression, as well as
interleukin (IL)-2 and
interferon (IFN)-γ levels, were up-regulated. However, 0.6 ng/day SEA did not cause discharge. Histological examination revealed prominent eosinophilic infiltration. ECP and GATA-3 expression, as well as
IL-4 and
IL-5 levels, were increased at this lower dose. In conclusion, SEA induces acute
rhinosinusitis associated with a Th1-type immune response at high dose, and a predominantly Th2-biased allergic
inflammation at low dose.