The efficiency of a vaccine largely depends on the appropriate targeting of the innate immune system, mainly through prolonged delivery of antigens and immunomodulatory substances to professional antigen-presenting cells in the lymphoid environment. Particulate antigens, such as virus-like particles (VLP) induce potent immune responses. However, little is known about the relative importance of direct drainage of free antigen to lymph nodes (LN) versus cellular transport and the impact of particle size on the process. Here, we show that nanoparticles traffic to the draining LN in a size-dependent manner. Whereas large particles (500-2000 nm) were mostly associated with dendritic cells (DC) from the injection site, small (20-200 nm) nanoparticles and VLP (30 nm) were also found in LN-resident DC and macrophages, suggesting free drainage of these particles to the LN. In vivo imaging studies in mice conditionally depleted of DC confirmed the capacity of small but not large particles to drain freely to the LN and demonstrated that DC are strictly required for transport of large particles from the injection site to the LN. These data provide evidence that particle size determines the mechanism of trafficking to the LN and show that only small nanoparticles can specifically target LN-resident cells.

A current paradigm in immunology is that the strength of T cell responses is governed by antigen dose, localization, and costimulatory signals. This study investigates the influence of antigen kinetics on CD8 T cell responses in mice. A fixed cumulative antigen dose was administered by different schedules to produce distinct dose-kinetics. Antigenic stimulation increasing exponentially over days was a stronger stimulus for CD8 T cells and antiviral immunity than a single dose or multiple dosing with daily equal doses. The same was observed for dendritic cell vaccination, with regard to T cell and anti-tumor responses, and for T cells stimulated in vitro. In conclusion, stimulation kinetics per se was shown to be a separate parameter of immunogenicity. These findings warrant a revision of current immunization models and have implications for vaccine development and immunotherapy.antigen presentation ͉ antiviral immunity ͉ CD8 T cell responses ͉ tumor vaccine

Iron is a critical metal for several vital biological processes. Most of the body’s iron is bound to hemoglobin in erythrocytes. Iron from senescent red blood cells is recycled by macrophages in the spleen, liver and bone marrow. Dietary iron is taken up by the divalent metal transporter 1 (DMT1) in enterocytes and transported to portal blood via ferroportin (FPN), where it is bound to transferrin and taken up by hepatocytes, macrophages and bone marrow cells via transferrin receptor 1 (TfR1). While most of the physiologically active iron is bound hemoglobin, the major storage of most iron occurs in the liver in a ferritin-bound fashion. In response to an increased iron load, hepatocytes secrete the peptide hormone hepcidin, which binds to and induces internalization and degradation of the iron transporter FPN, thus controlling the amount of iron released from the cells into the blood. This review summarizes the key mechanisms and players involved in cellular and systemic iron regulation.

SUMMARY SUMMARYProtective immunity is provided by the interplay between the innate and the adaptive arms of the immune systems. The innate as well as the adaptive immune response is regulated by specialized cells with the challenging task to eliminate pathogens while not damaging the host itself. Usually the immune system copes well with this charge, but is not always successful. Furthermore, proinflammatory lipids, cytokines, and chemokines are produced and released, leading to an allergic inflammation. Although frequency of individuals suffering from allergies has increased exponentially over the last century, the only available therapy that stops disease progression is allergen-specific immunotherapy (SIT). Even though allergenspecific antibodies have been reported to play an important role in SIT, mechanisms of IgGmediated inhibition of allergic reactions are not well defined.The present studies aimed to provide better understanding of the mechanisms how allergenspecific IgG antibodies may modulate allergic responses. Therefore, we generated monoclonal antibodies (mAbs) that recognize three non-overlapping epitopes on the major cat allergen Feld1. Each of the three mAbs was produced as IgE or different IgG isotypes. We found that IgE antibodies against two non-overlapping epitopes on Feld1 were required and sufficient to sensitize mast cells for maximal activation upon exposure to monomeric Feld1.

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