Interleukin-1 and estrogen protect against disseminating dentoalveolar infections

Dentoalveolar bacterial infections cause localized tissue and bone destruction, but usually remain well-localized within teeth in immunocompetent hosts. However, in certain cases these infections may invade head and neck tissues, resulting in orofacial abscesses, cellulitis and sepsis, with resultant high morbidity and even mortality. In the present studies, we developed a novel model of spreading dentoalveolar infections in mice by treatment with neutralizing antibodies against both interleukin-1α (IL-1α) and IL-1β. Surprisingly male but not female mice given anti-IL-1 antibodies developed orofacial abscesses, weight loss, splenomegaly and sepsis. Female mice developed abscesses and sepsis comparable to males following ovariectomy (OVX), which was reversed by estrogen supplementation. Anti-IL-1 blockade inhibited IL-12, interferon γ (IFNγ) and IL-6 but not IL-10 expression in infrabony lesions, suggestive of a local anti-inflammatory response. There was greater infiltration of neutrophils and other inflammatory cells into lesions in anti-IL-1-treated animals; however, blood leukocytes had reduced bacterial phagocytic and killing activity ex vivo. Estrogen directly stimulated IL-1 production by macrophages, suggesting that the resistance of females to disseminating dentoalveolar infections may be due to their heightened pro-inflammatory responses following bacterial challenge, leading to enhanced localization of these infections.