HLA class I receptors: molecules of the immunoglobulin superfamily (IgSF) called killer cell inhibitory receptors * Departments of Structural Biology and Microbiology and Immunology (KIR) are specific for determinants shared by subsets of HLA-B or -C allotypes (Colonna and Samaridis, 1995;

Natural killer (NK) cells and dendritic cells (DCs) are two distinct cell types of innate immunity. It is known that the in vitro interaction of human NK cells with autologous DCs results in DC lysis. Here we show that contact-dependent interactions between activated human NK cells and immature DCs (iDCs) provides a “control switch” for the immune system. At low NK/DC ratios, this interaction dramatically amplifies DC responses, whereas at high ratios it completely turns off their responses. Specifically, culture of activated human NK cells with iDCs, at low NK/DC ratios (1:5), led to exponential increases in DC cytokine production, which were completely dependent on cell-to-cell contact. DC maturation was also driven by cognate interactions with NK cells and maturation was dependent on endogenously produced TNF-α in the culture. At slightly higher NK/DC ratios (5:1), inhibition of DC functions was the dominant feature due to potent killing by the autologous NK cells. Resting NK cells also stimulated autologous DC maturation in a TNF-α/contact-dependent manner, however, increasing the NK/DC ratio only led to an enhancement of this effect.

Natural killer cell stimulatory factor or interleukin 12 (NKSF/IL-12) is a heterodimeric cytokine produced by monocytes/macrophages, B cells, and possibly other accessory cell types primarily in response to bacteria or bacterial products. NKSF/IL-12 mediates pleiomorphic biological activity on T and NK cells and, alone or in synergy with other inducers, is a powerful stimulator of interferon gamma (IFN-gamma) production. IL-10 is a potent inhibitor of monocyte-macrophage activation, that inhibits production of tumor necrosis factor alpha (TNF-alpha), IL-1 and also IFN-gamma from lymphocytes acting at the level of accessory cells. Because TNF-alpha and IL-1 are not efficient inducers of IFN-gamma, the mechanism by which IL-10 inhibits IFN-gamma production is not clear. In this paper, we show that IL-10 is a potent inhibitor of NKSF/IL-12 production from human peripheral blood mononuclear cells activated with Staphylococcus aureus or lipopolysaccharide (LPS). Both the production of the free NKSF/IL-12 p40 chain and the biologically active p70 heterodimer are blocked by IL-10. NKSF/IL-12 p40 chain mRNA accumulation is strongly induced by S. aureus or LPS and downregulated by IL-10, whereas the p35 mRNA is constitutively expressed and only minimally regulated by S. aureus, LPS, or IL-10. Although IL-10 is able to block the production of NKSF/IL-12, a powerful inducer of IFN-gamma both in vitro and in vivo, the mechanism of inhibition of IFN-gamma by IL-10 cannot be explained only on the basis of inhibition of NKSF/IL-12 because IL-10 can partially inhibit IFN-gamma production induced by NKSF/IL-12, and also, the IFN-gamma production in response to various stimuli in the presence of neutralizing antibodies to NKSF/IL-12. Our findings that antibodies against NKSF/IL-12, TNF-alpha, or IL-1 beta can significantly inhibit IFN-gamma production in response to various stimuli and that NKSF/IL-12 and IL-1 beta can overcome the IL-10-mediated inhibition of IFN-gamma, suggest that IL-10 inhibition of IFN-gamma production is primarily due to its blocking production from accessory cells of the IFN-gamma-inducer NKSF/IL-12, as well as the costimulating molecule IL-1 beta.

The expression of KIR and CD94:NKG2 receptors was determined for more than 100 natural killer (NK) cell clones obtained from two blood donors who differ in their HLA class I and KIR genes. More than 98% of the clones were inhibited by individual autologous class I allotypes, and every clone was inhibited by the combination of autologous allotypes. The patterns of inhibition correlate with expression of inhibitory receptors of defined specificity. One donor possesses three class I ligands for KIR, and a majority of NK cells use KIR as their inhibitory receptor; the second donor possesses only a single ligand for KIR, and a majority of NK cells use the more broadly reactive CD94:NKG2a as their inhibitory receptor. Because of these differences, the first donor has subpopulations of NK cells that kill cells of the second donor, whereas the NK cells of the second donor are universally tolerant of cells from the first donor.

Despite more than two decades of research and development on nucleic acid vaccines, there is still no commercial product for human use. Taking advantage of the recent innovations in systemic delivery of short interfering RNA (siRNA) using lipid nanoparticles (LNPs), we developed a self-amplifying RNA vaccine. Here we show that nonviral delivery of a 9-kb self-amplifying RNA encapsulated within an LNP substantially increased immunogenicity compared with delivery of unformulated RNA. This unique vaccine technology was found to elicit broad, potent, and protective immune responses, that were comparable to a viral delivery technology, but without the inherent limitations of viral vectors. Given the many positive attributes of nucleic acid vaccines, our results suggest that a comprehensive evaluation of nonviral technologies to deliver self-amplifying RNA vaccines is warranted.vaccine platform | SAM vaccine | respiratory syncytial virus | HIV