Antigen-pulsed dendritic cells (DCs) are used as natural adjuvants for vaccination, but the factors that influence the efficacy of this treatment are poorly understood. We investigated the parameters that affect the migration of subcutaneously injected mouse-mature DCs to the draining lymph node. We found that the efficiency of DC migration varied with the number of injected DCs and that CCR7+/+ DCs migrating to the draining lymph node, but not CCR7−/− DCs that failed to do so, efficiently induced a rapid increase in lymph node cellularity, which was observed before the onset of T cell proliferation. We also report that DC migration could be increased up to 10-fold by preinjection of inflammatory cytokines that increased the expression of the CCR7 ligand CCL21 in lymphatic endothelial cells. The magnitude and quality of CD4+ T cell response was proportional to the number of antigen-carrying DCs that reached the lymph node and could be boosted up to 40-fold by preinjection of tumor necrosis factor that conditioned the tissue for increased DC migration. These results indicate that DC number and tissue inflammation are critical parameters for DC-based vaccination.

Palonosetron exhibited allosteric binding and positive cooperativity when binding to the 5-HT(3) receptor. Palonosetron also triggered functional effects that persisted beyond its binding to the 5-HT(3) receptor at the cell surface. Differences in binding and effects on receptor function may be relevant to the unique beneficial actions of palonosetron. To our knowledge, this is the first report showing palonosetron's interaction with the 5-HT(3) receptor at the molecular level, clearly differentiating it from other 5-HT(3)-RAs.

The contribution of T helper (Th) and T cytotoxic (Tc) type 1 lymphocytes in the expression of allergic contact dermatitis to haptens has been amply documented. Conversely, the existence of T cell-based regulatory mechanisms has been poorly investigated. Here, we examined the properties of a subset of nickel-specific CD4+ T cells displaying the cytokine profile (IL-10 , IL-5 , IFN-gamma+/-, IL-4+/-) of T regulatory cells 1 (Tr1) and with the potential to down-modulate immune responses to nickel. Tr1 clones were isolated from skin challenged with NiSO4 and peripheral blood of nickel-allergic patients, and from the blood of healthy individuals. Tr1 clones expressed CD25, CD28, CD30, CD26, and the IL-12 receptor beta2 chain upon activation, whereas the lymphocyte activation antigen-3 was present on 50% of the clones. Monocytes precultured with Tr1 cells in the presence of nickel, or treated with Tr1-derived supernatant, exhibited a markedly diminished capacity to stimulate nickel-specific Th1 responses. Tr1 supernatants also blocked the differentiation of dendritic cells (DC) from monocytes, as well as DC maturation and IL-12 production induced by lipopolysaccharide. As a consequence, the ability of DC to stimulate nickel-specific Th1 and Tc1 responses was greatly impaired. These inhibitory effects were completely prevented by IL-10, but not IL-5, neutralization. In aggregate, the results indicate that Tr1 cells can potently regulate the expression of Th1-mediated allergic diseases via release of IL-10.

We have investigated the chemokine receptor expression and migratory behavior of a new subset of nickel-specific skin-homing regulatory CD4+ T cells (ThIL-10) releasing high levels of IL-10, low IFN-γ, and undetectable IL-4. These cells inhibit in a IL-10-dependent manner the capacity of dendritic cells to activate nickel-specific Tc1 and Th1 lymphocytes. RNase protection assay and FACS analysis revealed the expression of a vast repertoire of chemokine receptors on resting ThIL-10, including the Th1-associated CXCR3 and CCR5, and the Th2-associated CCR3, CCR4, and CCR8, the latter at higher levels compared with Th2 cells. The most active chemokines for resting ThIL-10, in terms of calcium mobilization and in vitro migration, were in order of potency: CCL2 (monocyte chemoattractant protein-1, CCR2 ligand), CCL4 (macrophage-inflammatory protein-1β, CCR5 ligand), CCL3 (macrophage-inflammatory protein-1α, CCR1/5 ligand), CCL17 (thymus and activation-regulated chemokine, CCR4 ligand), CCL1 (I-309, CCR8 ligand), CXCL12 (stromal-derived factor-1, CXCR4), and CCL11 (eotaxin, CCR3 ligand). Consistent with receptor expression down-regulation, activated ThIL-10 exhibited a reduced or absent response to most chemokines, but retained a significant migratory capacity to I-309, monocyte chemoattractant protein-1, and thymus and activation-regulated chemokine. I-309, which was ineffective on Th1 lymphocytes, attracted more efficiently ThIL-10 than Th2 cells. I-309 and CCR8 mRNAs were not detected in unaffected skin and were up-regulated at the skin site of nickel-allergic reaction, with an earlier expression kinetics compared with IL-10 and IL-4. Results indicate that skin-homing regulatory ThIL-10 lymphocytes coexpress functional Th1- and Th2-associated chemokine receptors, and that CCR8/I-309-driven recruitment of both resting and activated ThIL-10 cells may be critically involved in the regulation of Th1-mediated skin allergic disorders.

We investigated the capacity of CD25+ T regulatory cells (Treg) to modulate T cell responses to nickel, a common cause of allergic contact dermatitis. CD4+ T cells isolated from the peripheral blood of six healthy, nonallergic individuals showed a limited capacity to proliferate in response to nickel in vitro, but responsiveness was strongly augmented (mean increment ± SD, 240 ± 60%) when cells were depleted of CD25+ Treg. Although CD25+ Treg were anergic to nickel, a small percentage up-regulated membrane CTLA-4 upon nickel exposure. CD25+ Treg strongly and dose-dependently inhibited nickel-specific activation of CD25− T lymphocytes in coculture experiments in a cytokine-independent, but cell-to-cell contact-dependent, manner. Approximately 30% of circulating CD25+ Treg expressed the cutaneous lymphocyte-associated Ag (CLA), and CLA+CD25+ Treg were more efficient than CLA−CD25+ cells in suppressing nickel responsiveness of CD25− T cells. The site of a negative patch test in response to nickel showed an infiltrate of CD4+CLA+ cells and CD25+ cells, which accounted for ∼20% of the total T cells isolated from the tissue. Skin-derived T cells suppressed nickel-specific responses of peripheral blood CD25− T cells. In addition, 60 ± 14% of peripheral blood CD25+ Treg expressed the chemokine receptor CCR7 and strongly inhibited naive T cell activation in response to nickel. Finally, CD25+ T cells isolated from peripheral blood of nickel-allergic patients showed a limited or absent capacity to suppress metal-specific CD4+ and CD8+ T cell responses. The results indicates that in healthy individuals CD25+ Treg can control the activation of both naive and effector nickel-specific T cells.