TNF controls the infiltration of dendritic cells into the site of Leishmania major infection

TNF-negative C57BL/6 (B6.TNF−/−) mice are highly susceptible to Leishmania (L.) major infection and succumb rapidly to fatal leishmaniasis. A T helper type 1 (Th1) cell-mediated immune response is central for protective anti-leishmanial immunity. Therefore, the observed susceptibility of B6.TNF−/− mice to L. major parasites could be caused by a deficiency in mounting a Th1 response. Analysis of infected footpads revealed, that B6.TNF−/− mice exhibited a substantially diminished formation of DCs at the site of infection. Furthermore, Th1 cytokines such as IFN-γ were reduced in footpads of infected B6.TNF−/− mice. Cutaneous reconstitution of B6.TNF−/− mice with either bone marrow derived DCs (BM-DCs) or recombinant TNF simultaneous to infection resulted in an increased expression of cytokines such as IFN-γ and in an enhanced presence of Leishmania-antigen in skin draining lymph nodes. In addition, the individual time of survival was doubled. In conclusion we demonstrate that the expression of dermal TNF is necessary to provide an environment that initiates a local inflammatory response, but is not sufficient to induce protective immunity

Chemokine and chemotactic signals in dendritic cell migration

Dendritic cells (DCs) are professional antigen-presenting cells responsible for the activation of specific T-cell responses and for the development of immune tolerance. Immature DCs reside in peripheral tissues and specialize in antigen capture, whereas mature DCs reside mostly in the secondary lymphoid organs where they act as antigen-presenting cells. The correct localization of DCs is strictly regulated by a large variety of chemotactic and nonchemotactic signals that include bacterial products, DAMPs (danger-associated molecular patterns), complement proteins, lipids, and chemokines. These signals function both individually and in concert, generating a complex regulatory network. This network is regulated at multiple levels through different strategies, such as synergistic interactions, proteolytic processing, and the actions of atypical chemokine receptors. Understanding this complex scenario will help to clarify the role of DCs in different pathological conditions, such as autoimmune diseases and cancers and will uncover new molecular targets for therapeutic interventions. © 2018 CSI and USTC