We have identified two cell subsets in human blood based on the lack of lineage markers (lin-) and the differential expression of immunoglobulin-like transcript receptor 1 (ILT1) and ILT3. One subset (lin-/ILT3+/ILT1+) is related to myeloid dendritic cells. The other subset (lin-/ILT3+/ILT1+) corresponds to 'plasmacytoid monocytes'. These cells are found in inflamed lymph nodes in and around the high endothelial venules. They express CD62L and CXCR3, and produce extremely large amounts of type I interferon after stimulation with influenza virus or CD40L. These results, with the distinct cell phenotype, indicate that plasmacytoid monocytes represent a specialized cell lineage that enters inflamed lymph nodes at high endothelial venules, where it produces type I interferon. Plasmacytoid monocytes may protect other cells from viral infections and promote survival of antigen-activated T cells.

2B4 is a cell surface glycoprotein of the immunoglobulin superfamily structurally related to CD2-like molecules. It was originally identified in the mouse as a receptor that mediates non-MHC-restricted cytotoxicity by NK cells and CD8 + T cells. Recently, 2B4 was shown to bind CD48 by molecular binding assays and surface plasmon resonance. Here, we have investigated the cell surface expression, biochemical characteristics and function of human 2B4. Our results show that 2B4 is expressed not only on NK cells and CD8 + T cells, but also on monocytes and basophils, indicating a broader role for 2B4 in leukocyte activation. In NK cells, engagement of 2B4 with a specific monoclonal antibody or with CD48 can trigger NK cell-mediated cytotoxicity. The contribution of 2B4-CD48 interaction to target cell lysis by different NK cell clones varies, probably dependent on the relative contribution of other receptor-ligand interactions. In T cells and monocytes, ligation of 2B4 does not lead to T cell or monocyte activation. Thus, it appears that the primary function of 2B4 is to modulate other receptor-ligand interactions to enhance leukocyte activation.

A significant breakthrough in the nitride chemistry of main group elements has been achieved: Surprisingly Sn3N4, for which there had been no proof of existence until now, as well as the isotypic high‐pressure polymorphs γ‐Si3N4 and γ‐Ge3N4 have been synthesized. All three compounds crystallize in a spinel structure type (see picture) that previously has not been found for nitrides, and may have a high relevance for practical applications in the context of ultrahard materials.

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