Secreted ß3-integrin enhances natural killer cell activity against acute myeloid leukemia cells.

Integrins are a large family of heterodimeric proteins that are involved in cell adhesion, migration, and proliferation. Integrin diversity and function is regulated by alternative splicing. Membrane-bound and truncated ß3-integrins were shown to be key players in cancer metastasis. However, the immunomodulatory functions of the soluble (s) ß3-integrin have not been investigated yet. In this study, we described a novel form of sß3-integrin in acute myeloid leukaemia (AML) patients. Furthermore, we assessed the role of the sß3-integrin in the modulation of natural killer (NK)-cell activity. Levels of sß3-integrin were analysed in plasma samples of 23 AML patients and 26 healthy donors by ELISA. The capacity of sß3-integrin to regulate NK cell activity was investigated using proliferation, cytokine secretion, and cytotoxicity assays. Circulating sß3-integrin was detected in the plasma of 8 AML patients. NK cells showed significantly higher proliferation rates after stimulation with sß3-integrin and IL-2, IL-15 (73%). Significant increases in the NK cells' secreted levels of TNF-α, IFN-γ were measured in presence of sß3-integrin. In addition, sß3-integrin caused the upregulation of Granzyme B transcripts levels as well as FasL expression levels in NK cells. Most importantly, significantly higher K562 or AML blast target cell lysis rates were observed when NK cells were exposed to sß3-integrin. This study reports the identification of a novel sß3-integrin in AML patients and provides novel insights into its role in the immunomodulation of NK cell activity.

Semaphorin 3A alters endothelial cell immunogenicity by regulating Class II transactivator activity circuits.

BACKGROUND: Endothelial cells (ECs) play a pivotal role in the allogeneic immune response upon transplantation. Semaphorin 3A (Sema3A) was implicated in the modulation of EC growth, but its effects on immunogenicity were not previously investigated. STUDY DESIGN AND METHODS: ECs were transduced with a lentiviral vector encoding for the green fluorescence protein (GFP) sequence under the control of a Class II transactivator (CIITA)-dependent promoter. Upon stimulation of nonmodified ECs with recombinant Sema3A protein, mRNA and protein levels of CIITA, HLA-DR, and Sema3A receptors were evaluated. An enzyme-linked immunosorbent assay was developed to quantify Sema3A levels in the sera of kidney-transplanted patients. RESULTS: Sema3A stimulation of lentiviral vector encoding for the GFP sequence ECs caused a significant up regulation of the transgene expression, indicating an increase in CIITA levels. Stimulation of nonmodified ECs with Sema3A resulted in an up regulation of CIITA expression, which was associated with enhanced HLA-DR levels and an increase in alloreactive CD4+ T-cell proliferation. Sema3A receptor expression was enhanced by CIITA, establishing a positive feedback loop. Higher levels of Sema3A were observed in sera of patients presenting with organ rejection. CONCLUSION: This study links Sema3A signaling in ECs with increased CIITA levels and higher HLA-DR expression, resulting in CD4+ T-cell activation, which might have important implications for tissue and organ transplantation.

Development of a single-antigen magnetic bead assay (SAMBA) for the sensitive detection of HPA-1a alloantibodies using tag-engineered recombinant soluble ß3 integrin.

Timely and accurate testing for human platelet antigen 1a (HPA-1a) alloantibodies is vital for clinical diagnosis of neonatal alloimmune thrombocytopenia (NAIT). Current antigen-specific assays used for the detection of HPA-1 alloantibodies are technically very complex and cumbersome for most diagnostic laboratories. Hence, we designed and applied recombinant soluble (rs) ß3 integrins displaying HPA-1a or HPA-1b epitopes for the development of a single-antigen magnetic bead assay (SAMBA). Soluble HPA-1a and HPA-1b were produced recombinantly in human embryonic kidney 293 (HEK293) cells and differentially tagged. The recombinant soluble proteins were then immobilized onto paramagnetic beads and used for analysis of HPA-1 alloantibodies by enzyme-linked immunosorbent assay (ELISA). HPA-1a serum samples (n=7) from NAIT patients, inert sera and sera containing non-HPA-1a antibodies were used to evaluate the sensitivity and specificity of the SAMBA. Fusion of V5-His or GS-SBP-His tags to the rsß3 integrins resulted in high-yield expression. SAMBA was able to detect all HPA-1a and -1b alloantibodies recognized by monoclonal antibody-specific immobilization of platelet antigens assay (MAIPA). No cross-reactions between the sera were observed. Two out of seven of the HPA-1a alloantibody-containing sera demonstrated weak to moderate reactivity in MAIPA but strong signals in SAMBA. SAMBA provides a very reliable method for the detection of HPA-1 antibodies with high specificity and sensitivity. This simple and rapid assay can be adapted for use in any routine laboratory and can be potentially adapted for use on automated systems.

Plasmid incidence in the subgroups of two bacterial communities.

The plasmid incidence of two bacterial communities from soil and freshwater was determined by endogenous plasmid isolation. The overall plasmid incidence for the communities was about 10%, while the frequency of plasmid-containing members in different subgroups ranged from 0% to 100%. Both communities included a minor population where all members contained several plasmids.

A functional plasmid-borne rrn operon in soil isolates belonging to the genus Paracoccus.

Plasmid analysis of isolates from a small Paracoccus population revealed that all 15 representatives carried at least one endogenous plasmid of 23 or 15 kb in size, in addition to further plasmids of different sizes. It was shown by restriction analysis and hybridization that the 23 and 15 kb plasmids from the different isolates were identical or very similar to each other. By partial sequencing of pOL18/23, one of the 23 kb plasmids, a complete rrn operon with the structural genes for 16S, 23S and 5S rRNA, two genes for tRNA(Ile) and tRNA(Ala) within the spacer between the 16S and 23S rRNA genes, and a final tRNA(fMet) at the end of the operon were discovered. Expression of a green fluorescent protein gene (gfp) after insertion of a DNA fragment from the region upstream of the rRNA genes into a promoter-probe vector demonstrated that the rrn promoter region is functional. The rrn operon encoded by plasmid pOL18/23 is the first complete rrn operon sequenced from a strain of the genus Paracoccus, and only the second example of an rrn operon on a small plasmid.