A novel dendritic cell (DC)-

Three surface molecules of mouse CD8+ dendritic cells (DCs), also found on the equivalent human DC subpopulation, were compared as targets for Ab-mediated delivery of Ags, a developing strategy for vaccination. For the production of cytotoxic T cells, DEC-205 and Clec9A, but not Clec12A, were effective targets, although only in the presence of adjuvants. For Ab production, however, Clec9A excelled as a target, even in the absence of adjuvant. Potent humoral immunity was a result of the highly specific expression of Clec9A on DCs, which allowed longer residence of targeting Abs in the bloodstream, prolonged DC Ag presentation, and extended CD4 T cell proliferation, all of which drove highly efficient development of follicular helper T cells. Because Clec9A shows a similar expression pattern on human DCs, it has particular promise as a target for vaccines of human application.

The immune system must distinguish viable cells from cells damaged by physical and infective processes. The damaged cell-recognition molecule Clec9A is expressed on the surface of the mouse and human dendritic cell subsets specialized for the uptake and processing of material from dead cells. Clec9A recognizes a conserved component within nucleated and nonnucleated cells, exposed when cell membranes are damaged. We have identified this Clec9A ligand as a filamentous form of actin in association with particular actin-binding domains of cytoskeletal proteins. We have determined the crystal structure of the human CLEC9A C-type lectin domain and propose a functional dimeric structure with conserved tryptophans in the ligand recognition site. Mutation of these residues ablated CLEC9A binding to damaged cells and to the isolated ligand complexes. We propose that Clec9A provides targeted recruitment of the adaptive immune system during infection and can also be utilized to enhance immune responses generated by vaccines.

Synthetic CpG oligonucleotides (ODN) have potent immunostimulatory properties exploited in clinical vaccine trials. How CpG ODN are captured and delivered to the intracellular receptor TLR9, however, has been elusive. Here we show that DEC-205, a multilectin receptor expressed by a variety of cells, is a receptor for CpG ODN. When CpG ODN are used as an adjuvant, mice deficient in DEC-205 have impaired dendritic cell (DC) and B-cell maturation, are unable to make some cytokines such as IL-12, and display suboptimal cytotoxic T-cell responses. We reveal that DEC-205 directly binds class B CpG ODN and enhances their uptake. The CpG-ODN binding function of DEC-205 is conserved between mouse and man, although human DEC-205 preferentially binds a specific class B CpG ODN that has been selected for human clinical trials. Our findings identify an important receptor for class B CpG ODN and reveal a unique function for DEC-205.

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A normalized subtracted gene expression library was generated from freshly isolated mouse dendritic cells (DC) of all subtypes, then used to construct cDNA microarrays. The gene expression profiles of the three splenic conventional DC (cDC) subsets were compared by microarray hybridization and two genes encoding signal regulatory protein β (Sirpβ1 and Sirpβ4) molecules were identified as differentially expressed in CD8− cDC. Genomic sequence analysis revealed a third Sirpβ member localized in the same gene cluster. These Sirpβ genes encode cell surface molecules containing extracellular Ig domains and short intracytoplasmic domains that have a charged amino acid in the transmembrane region which can potentially interact with ITAM-bearing molecules to mediate signaling. Indeed, we demonstrated interactions between Sirpβ1 and β2 with the ITAM-bearing signaling molecule Dap12. Real-time PCR analysis showed that all three Sirpβ genes were expressed by CD8− cDC, but not by CD8+ cDC or plasmacytoid pre-DC. The related Sirpα gene showed a similar expression profile on cDC subtypes but was also expressed by plasmacytoid pre-DC. The differential expression of Sirpα and Sirpβ1 molecules on DC was confirmed by staining with mAbs, including a new mAb recognizing Sirpβ1. Cross-linking of Sirpβ1 on DC resulted in a reduction in phagocytosis of Leishmania major parasites, but did not affect phagocytosis of latex beads, perhaps indicating that the regulation of phagocytosis by Sirpβ1 is a ligand-dependent interaction. Thus, we postulate that the differential expression of these molecules may confer the ability to regulate the phagocytosis of particular ligands to CD8− cDC.

H]arginine binding to BA 9 did not differ between groups, and there was no specific binding of [ 3 H]raclopride or 7-hydroxy-2-(di-n-[ 3 H]propylamino)tetralin to BA 9 from either cohort of subjects. This suggests the density of dopamine D 1 -like and NMDA receptors, the dopamine transporter, and nitric oxide synthase activity are not altered in BA 9 from schizophrenic subjects. The selective nature of the changes in serotonin 2A and GABA A receptors in DLPFC could indicate that these changes are involved in the pathology of schizophrenia.

Local production of a single Ab against T cells can reduce graft infiltration at the xenograft site and may reduce the need for conventional, systemic immunosuppression.