Dendritic cells retrovirally overexpressing IL-12 induce strong Th1 responses to inhaled antigen in the lung but fail to revert established Th2 sensitization

Abstract

It has been postulated that low-level interleukin (IL)-12 production of antigen-presenting cells is associated with the risk of developing atopic asthma. To study the relationship between IL-12 production capacity of dendritic cells (DCs) and development of T helper type 2 (Th2) responses in the lung, we genetically engineered DCs to constutively overexpress bioactive IL-12. Retrovirally mediated overexpression of IL-12 in DCs strongly polarized naive ovalbumin (OVA)-specific CD4+ T cells toward Th1 effector cells in vitro. After intratracheal injection, OVA-pulsed IL-12-overexpressing DCs failed to induce Th2 responses in vivo and no longer primed mice for Th2-dependent eosinophilic airway inflammation upon OVA aerosol challenge, readily observed in mice immunized with sham-transfected, OVA-pulsed DCs. Analysis of a panel of cytokines and chemokines in the lung demonstrated that the lack of Th2 sensitization was accompanied by increased production of the Th1 cytokine interferon-gamma (IFN-gamma), chemokines induced by IFN-gamma, and the immunoregulatory cytokine IL-10. When Th2 priming was induced using OVA/alum prior to intratracheal DC administration, DCs constitutively expressing IL-12 were no longer capable of preventing eosinophilic airway inflammation and even enhanced it. These data show directly that high-level expression of IL-12 in DCs prevents the development of Th2 sensitization. Enhancing IL-12 production in DCs should be seen as a primary prevention strategy for atopic disorders. Enhancing IL-12 production in DCs is less likely to be of benefit in already Th2-sensitized individuals.

IL-12-Impaired and IL-12-Secreting Dendritic Cells Produce IL-23 upon CD154 Restimulation

“…The results of our recall assays furthermore demonstrate that T cells stimulated by autologous Ag-loaded DCs express CD154 and may thus bypass the p38 MAPK pathway (43). In Th2 immunity, IL-12-overexpressing DCs prevented the development of Th2 pathology in murine allergic lung disease but could not reduce preexisting eosinophilic airway inflammation, which was even enhanced (63). Collectively, the data indicate that IL-12-impaired DCs cannot be used therapeutically to silence or reverse preexisting Th1 immune responses in vivo (e.g., in autoimmune diseases).…”

Cytokine gene-modulated dendritic cells protect against allergic airway inflammation by inducing IL-10+IFN-γ+CD4+ T cells

“…Therefore, genetically modulated DCs, such as IL-12, were tested to see whether they could counterbalance Th2 activity. 24,25 These strategies proved to be efficient in inhibiting the induction of antigeninduced Th2 responses, but they had a major drawback of causing Th1-driven inflammatory pulmonary pathology. However, although Th1 cells might not function in the lung mucosa itself to inhibit allergic asthma, it is possible that Th1 cells might act in peripheral lymphoid organs to inhibit the early development of Th2 effector cells.…”

Lyn-Deficient Mice Develop Severe, Persistent Asthma: Lyn Is a Critical Negative Regulator of Th2 Immunity

“…IL-12 is critical for Th1 cytokine responses and considered an inhibitory factor for allergic responses and Th2 cytokine production. Indeed, it has been shown recently that overexpression of IL-12 by DCs strongly polarized naive OVA-specific CD4 ϩ T cells toward a Th1 phenotype in vitro and in vivo, and these DCs failed to induce eosinophilic airway inflammation (38). Therefore, we measured IL-12 production by Lyn Ϫ/Ϫ DCs in response to LPS and found it to be impaired compared with control DCs (Fig.…”