The signalling imprints of nanoparticle uptake by bone marrow derived dendritic cells.

Nanoparticles (NP) possess remarkable adjuvant and carrier capacity, therefore are used in the development of various vaccine formulations. Our previous studies demonstrated that inert non-toxic 40-50 nm polystyrene NP (PS-NP) can promote strong CD8 T cell and antibody responses to the antigen, in the absence of observable inflammatory responses. Furthermore, instillation of PS-NP inhibited the development of allergic airway inflammation by induction of an immunological imprint via modulation of dendritic cell (DC) function without inducing oxidative stress in the lungs in mice. This is in contrast to many studies which show that a variety of ambient and man-made NP promote lung immunopathology, raising concerns generally about the safe use of NPs in biomedicine. Most NPs are capable of inducing inflammatory pathways in DC largely mediated by signalling via the extracellular signal-regulated kinase 1/2 (ERK). Herein, we investigate whether PS-NPs also activate ERK in DC in vitro. Our data show that PS-NP do not induce ERK activation in two different types of bone marrow derived (BM) DC cultures (expanded with GM-CSF or with GM-CSF together with IL-4). The absence of such signalling was not due to lack of PS-NP uptake by BM-DC as confirmed by confocal microscopy and flow cytometry. The process of NP uptake by DC usually initiates ERK signalling, suggesting an unusual uptake pathway may be engaged by PS-NPs. Indeed, data herein showns that uptake of PS-NP by BM-DC was substantially inhibited by phorbol myristate acetate (PMA) but not cytochalasin D (CCD), suggesting an uptake pathway utilising caveole for PS-NP. Together these data show that BM-DC take up PS-NP via a caveole-dependent pathway which does not trigger ERK signalling which may explain their efficient uptake by DC, without the concomitant activation of conventional inflammatory pathways.

Activated human T cells secrete exosomes that participate in IL-2 mediated immune response signaling.

It has previously been shown that nano-meter sized vesicles (30-100 nm), exosomes, secreted by antigen presenting cells can induce T cell responses thus showing the potential of exosomes to be used as immunological tools. Additionally, activated CD3⁺ T cells can secrete exosomes that have the ability to modulate different immunological responses. Here, we investigated what effects exosomes originating from activated CD3⁺ T cells have on resting CD3⁺ T cells by studying T cell proliferation, cytokine production and by performing T cell and exosome phenotype characterization. Human exosomes were generated in vitro following CD3⁺ T cell stimulation with anti-CD28, anti-CD3 and IL-2. Our results show that exosomes purified from stimulated CD3⁺ T cells together with IL-2 were able to generate proliferation in autologous resting CD3⁺ T cells. The CD3⁺ T cells stimulated with exosomes together with IL-2 had a higher proportion of CD8⁺ T cells and had a different cytokine profile compared to controls. These results indicate that activated CD3⁺ T cells communicate with resting autologous T cells via exosomes.