Identification of Novel Human Aggrecan T Cell Epitopes in HLA-B27 Transgenic Mice Associated with Spondyloarthropathy

The pathology of ankylosing spondylitis, reactive arthritis, and other spondyloarthropathies (SpA) is closely associated with the human leukocyte class I Ag HLA-B27. A characteristic finding in SpA is inflammation of cartilage structures of the joint, in particular at the site of ligament/tendon and bone junction (enthesitis). In this study, we investigated the role of CD8+ T cells in response to the cartilage proteoglycan aggrecan as a potential candidate autoantigen in BALB/c-B27 transgenic mice. We identified four new HLA-B27-restricted nonamer peptides, one of them (no. 67) with a particularly strong T cell immunogenicity. Peptide no. 67 immunization was capable of stimulating HLA-B27-restricted, CD8+ T cells in BALB/c-B27 transgenic animals, but not in wild-type BALB/c mice. The peptide was specifically recognized on P815-B27 transfectants by HLA-B27-restricted CTLs, which were also detectable by HLA tetramer staining ex vivo as well as in situ. Most importantly, analysis of the joints from peptide no. 67-immunized mice induced typical histological signs of SpA. Our data indicate that HLA-B27-restricted epitopes derived from human aggrecan are involved in the induction of inflammation (tenosynovitis), underlining the importance of HLA-B27 in the pathogenesis of SpA.

Truncated HLA-G isoforms are retained in the endoplasmic reticulum and insufficiently provide HLA-E ligands

The preferential expression of the non-polymorphic human leukocyte antigen G (HLA-G) on invading extravillous cytotrophoblast cells that are, with the exception of HLA-C and -E, HLA class I negative led to the hypothesis that HLA-G plays a major role in controlling the effector functions of the large granular leukocytes (LGL), a specialized natural killer (NK) cell population present in large numbers in the decidua. Transcription of the HLA-G gene is characterized by extensive alternative splicing producing at least seven potentially membrane bound or secreted isoforms. Except for HLA-G1 and its soluble variant (HLA-G1s), there is still dispute as to whether any of the other isoforms displays a major immunological function. Here we describe that the membrane-bound isoforms HLA-G2, -G3, and G4 as well as the soluble variant of HLA-G2 (HLA-G2s) do not egress the endoplasmic reticulum as determined by Endo H sensitivity assays. Moreover these isoforms seem not to have a major immunological function with respect to NK cell inhibition by providing a ligand for HLA-E, which would allow the interaction of this molecule with the inhibitory CD94/NKG2A NK cell receptor.

Renal cell carcinoma-infiltrating natural killer cells express differential repertoires of activating and inhibitory receptors and are inhibited by specific HLA class I allotypes

Among tumor-infiltrating lymphocytes (TILs) directly isolated from renal cell carcinomas (RCCs), we found substantial numbers of natural killer (NK) cells in most tumor tissues. They could be identified reliably in situ with an antibody directed against the activating receptor (AR) NKp46 that is exclusively expressed by all NK cells. NK-enriched TILs (NK-TILs) showed cytotoxicity against major histocompatibility complex (MHC) class I-negative cell lines. The ability to detect lysis of target cells was dependent on the percentage of NK cells within the TILs, and cytotoxicity was only observed after overnight activation with low-dose interleukin-2 (IL-2). Infiltrating NK cells were found to express various inhibitory receptors (IRs); among these the CD94/NKG2A receptor complex was overrepresented compared to the autologous peripheral blood mononuclear cell (PBMC) population. Other IRs were underrepresented, indicating that NK subpopulations vary in their tumor-infiltrating capacity. IRs expressed by NK-TILs are functional since receptor engagement with MHC class I ligands presented by human leukocyte antigen (HLA)-transfected target cell lines was able to inhibit NK-mediated cytotoxicity. NK-TILs were also able to lyse autologous or allogeneic tumor cell lines in vitro. This activity correlated with low HLA class I surface expression since lysis could be inhibited by interferon (IFN)-gamma-expressing RCC transductants that displayed a higher surface density of HLA class I molecules. Therefore, NK cells infiltrating tumor tissues have an inherent ability to recognize transformed cells, but they require cytokine activation and are sensitive to inhibition by IR ligands.

HLA-G modulates immune responses by diverse receptor interactions

HLA-G regulates immune responses as it binds different receptors expressed on natural killer (NK) cells, T cells and myeloid cells. HLA-G1 can inhibit NK- and T-cell-mediated lysis of target cells by its interaction with the inhibitory receptors ILT2 and ILT4. Engaging KIR2DL4 triggers different reactions depending on the activation state of the effector cells. The indirect recognition of HLA-G as peptide presented by HLA-E and recognized by the CD94/NKG2 receptor family might further power the battle between the immune system and tumor cells. Secreted HLA-G5 can also bind CD8 and induces Fas/Fas ligand-mediated apoptosis in activated CD8+ lymphocytes.

The human SPANX multigene family: genomic organization, alignment and expression in male germ cells and tumor cell lines

Multigenicity is one of the features of cancer/testis-associated genes. In the present study we analyzed the number and expression of genes of the SPANX(CTp11) family of cancer/testis-associated genes. Genomic database analysis, next to the four previously described SPANX genes, revealed the presence of a novel gene: SPANXE. Moreover, we detected an allelic variant of SPANXB resulting in one amino acid substitution in the encoded protein: SPANXB'. Most SPANX genes are present on contig NT_011574 located at Xq26.3-Xq27.1. Based on expressed sequence tag databases and RT-PCR analysis three additional novel SPANX sequences were identified, though not represented so far in the human genome sequence. Sequence alignments justify a subdivision of this gene family based on the absence (SPANXA-likes) or presence (SPANXB) of an 18 base pair sequence stretch in the open reading frame. The alignments also reveal an unusually high level (99%) of intron homology. Furthermore, the nucleotide variations in the open reading frame almost all lead to amino acid substitutions. Southern blot and database analyses indicate that SPANX sequences are exclusively present in primates. With RT-PCR analysis on human sperm cell precursors and tumor cell lines most family members could be detected. SPANXB was only found in sperm cell precursors and could not be detected in the tumor cell lines tested. Overall SPANXA was the most frequently expressed SPANX variant in melanoma and glioblastoma cell lines.

HCMV glycoprotein US6 mediated inhibition of TAP does not affect HLA-E dependent protection of K-562 cells from NK cell lysis

Human cytomegalovirus has evolved multiple strategies to interfere with immune recognition by the host. A variety of mechanisms affect antigen presentation by major histocompatibility complex class I molecules resulting in a reduced class I cell-surface expression. This downregulation is expected to trigger natural killer (NK) cytotoxicity, requiring counteraction by the virus to establish long-term infection. Here we describe that the human cytomegalovirus gpUS6 protein, which has been demonstrated to downregulate the expression of human leukocyte antigen (HLA) class I and the presentation of cytotoxic T lymphocyte epitopes by blocking transporter associated with antigen presentation (TAP function), does not affect the ability of HLA-E to inhibit NK cell mediated lysis of K-562 cells by interaction with CD94/NKG2A expressed on NK cells. Cell surface expression and function of HLA-E is not altered although gpUS6 inhibits TAP-dependent peptide transport by 95%. Moreover, HLA-E molecules presenting HLA class I signal sequence-derived peptides are functionally detectable on transfected TAP-deficient RMA-S cells.

The non-classical MHC molecule HLA-G protects human muscle cells from immune-mediated lysis: implications for myoblast transplantation and gene therapy

HLA-G is a non-classical MHC class I molecule with highly limited tissue distribution which has been attributed chiefly immune-regulatory functions. We previously have reported that HLA-G is expressed in inflamed muscle in vivo and by cultured myoblasts in vitro. Here, we used the in vitro models of human myoblasts or TE671 muscle rhabdomyosarcoma cells to characterize the functional role of HLA-G for muscle immune cell interactions. Gene transfer of the two major isoforms of HLA-G (transmembranous HLA-G1 and soluble HLA-G5) into TE671 rendered these cells resistant to alloreactive lysis by direct inhibition of natural killer (NK) cells, and CD4 and CD8 T cells. Further, HLA-G reduced alloproliferation, interfered with effective priming of antigen-specific cytotoxic T cells and reduced antigen-specific alloreactive lysis. HLA-G pre-induced on cultured myoblasts inhibited lysis by alloreactive peripheral blood mononuclear cells. This protection was reversed by a neutralizing HLA-G antibody. Interestingly, a few HLA-G-positive cells within a population of HLA-G-negative muscle target cells conveyed significant inhibitory effects on alloreactive lysis. Our results reveal further insights into the immunobiology of muscle and suggest that ectopic expression of HLA-G may promote the survival of transplanted myoblasts in the future treatment of hereditary muscle diseases. Further, HLA-G could represent a novel self-derived anti-inflammatory principle applicable in strategies against inflammatory aggression.

Binding analysis of HLA-G specific antibodies to hematopoietic cells isolated from leukemia patients

Expression of HLA-G on the surface of malignant hematopoietic cells isolated from leukemia patients was analyzed by flow cytometry using monoclonal antibodies (mAbs) recognizing both, intact HLA-G complex (87G, 01G and MEM-G9) as well as HLA-G free heavy chain (4H84, MEM-G/1 and MEM-G/2). Prerequisite of HLA-G detection by mAbs specific to free heavy chain was mild acid treatment, which dissociates intact HLA-G complex. All mAbs, with the exception of 4H84 mAb, did not indicate the presence of HLA-G antigen in leukemia cells. Positive staining with 4H84 mAb was detected in acid-treated cells isolated from 16 out of 30 patients. Intensity of staining increased after IFN-g pre-incubation in most cases. Immunoblot analyses and RT-PCR, however, failed to detect HLA-G antigen or HLA-G transcripts in cells that bind 4H84 mAb after acid-treatment. The binding of 4H84 mAb can be explained by the acid-induced cross-reactivity of this HLA-G specific mAb with classical HLA class I molecules [15]. The results described here further demonstrate that the HLA-G molecule is not expressed in freshly isolated human leukemia cells.

NK cell activity during human cytomegalovirus infection is dominated by US2-11-mediated HLA class I down-regulation

A highly attractive approach to investigate the influence and hierarchical organization of viral proteins on cellular immune responses is to employ mutant viruses carrying deletions of various virus-encoded, immune-modulating genes. Here, we introduce a novel set of deletion mutants of the human CMV (HCMV) lacking the UL40 region either alone or on the background of a deletion mutant devoid of the entire US2-11 region. Deletion of UL40 had no significant effect on lysis of infected cells by NK cells, indicating that the expected enhancement of HLA-E expression by specific peptides derived from HCMV-encoded gpUL40 leader sequences was insufficient to confer target cell protection. Moreover, the kinetics of MHC class I down-regulation by US2-11 genes observed at early and late phases postinfection with wild-type virus correlated with increased susceptibility to NK lysis. Thus, the influence of HCMV genes on NK reactivity follows a hierarchy dominated by the US2-11 region, which encodes all viral genes capable of down-modulating expression of classical and non-classical MHC class I molecules. The insights gained from studies of such virus mutants may impact on future therapeutic strategies and vaccine development and incorporate NK cells in the line of defense mechanisms against HCMV infection.

A functional role of HLA-G expression in human gliomas: an alternative strategy of immune escape

HLA-G is a nonclassical MHC molecule with highly limited tissue distribution that has been attributed chiefly immune regulatory functions. Glioblastoma is paradigmatic for the capability of human cancers to paralyze the immune system. To delineate the potential role of HLA-G in glioblastoma immunobiology, expression patterns and functional relevance of this MHC class Ib molecule were investigated in glioma cells and brain tissues. HLA-G mRNA expression was detected in six of 12 glioma cell lines in the absence of IFN-gamma and in 10 of 12 cell lines in the presence of IFN-gamma. HLA-G protein was detected in four of 12 cell lines in the absence of IFN-gamma and in eight of 12 cell lines in the presence of IFN-gamma. Immunohistochemical analysis of human brain tumors revealed expression of HLA-G in four of five tissue samples. Functional studies on the role of HLA-G in glioma cells were conducted with alloreactive PBMCs, NK cells, and T cell subpopulations. Expression of membrane-bound HLA-G1 and soluble HLA-G5 inhibited alloreactive and Ag-specific immune responses. Gene transfer of HLA-G1 or HLA-G5 into HLA-G-negative glioma cells (U87MG) rendered cells highly resistant to direct alloreactive lysis, inhibited the alloproliferative response, and prevented efficient priming of cytotoxic T cells. The inhibitory effects of HLA-G were directed against CD8 and CD4 T cells, but appeared to be NK cell independent. Interestingly, few HLA-G-positive cells within a population of HLA-G-negative tumor cells exerted significant immune inhibitory effects. We conclude that the aberrant expression of HLA-G may contribute to immune escape in human glioblastoma.

Th1- and Th2-like cytokine production by first trimester decidual large granular lymphocytes is influenced by HLA-G and HLA-E

During normal early pregnancy, a particular immune environment in the decidua and the expression of non-classical HLA-G and HLA-E molecules on the invading trophoblast are assumed to be essential for the tolerance of the fetus. To assess whether HLA-G and HLA-E influence the cytokine production of their putative target cells [large granular lymphocytes (LGL)], we analysed the concentrations of tumour necrosis factor (TNF-alpha), interferon (IFN)-gamma, interleukin (IL)-10, IL-13 and granulocyte-macrophage colony stimulating factor (GM-CSF) in supernatants of isolated first trimester LGL co-cultured with HLA-G or HLA-E transfected K-562 leukaemia cells lacking the classical HLA class I and II molecules. In comparison with that observed with untransfected K-562 cells, co-culture of LGL with HLA-G-expressing cells significantly reduced the concentration of all cytokines investigated (TNF-alpha, IL-10 and GM-CSF, P < 0.01; IFN-gamma and IL-13, P < 0.05). In contrast, co-culture of LGL with HLA-E-expressing cells significantly (P < 0.01) decreased only IL-10 production, although a strong tendency towards reduced IL-13 levels was also observed. In the co-culture system presented, membrane-bound HLA-G and, to a lesser extent, HLA-E expression affected cytokine release by decidual LGL in a manner not consistent with the Th1/Th2 paradigm. In conclusion, our data are indicative of a general immune-suppressive effect of HLA-G on LGL activity.

Retaliation against tumor cells showing aberrant HLA expression using lymphokine activated killer-derived T cells

Lymphokine activated killer (LAK) cells represent mixtures of natural killer (NK) and non-MHC-restricted CTLs that have the capacity to lyse a variety of tumor cells and MHC class I-negative target cells. Although it is clear that NK cells are negatively regulated by interactions with MHC class Ia or class Ib molecules, the regulation of LAK-derived T cells has not been clarified to date. In the studies presented here, we demonstrate that IFN-gamma treatment of tumor cells can induce their resistance to LAK-derived T cells in a manner similar to that seen for NK cells. The IFN-gamma-mediated suppression of LAK activity correlates with increased MHC class I expression by the tumor cells, and the inhibition of LAK-mediated cytotoxicity can be reversed in the presence of class I-specific antibody. Furthermore, the expression of MHC class Ia or class Ib molecules in class I-negative cell lines can reduce their susceptibility to LAK-mediated cytotoxicity. This principle of negative regulation by MHC class I molecules applies to LAK-derived T cells generated from peripheral blood lymphocytes of renal cell carcinoma patients and healthy, control donors. Although LAK-derived T cells can be inhibited in their lytic activity through interactions with MHC class Ia and class Ib molecules, they do not express the known inhibitory receptors specific for these ligands that are found on NK cells. Apparently, LAK-derived T cells are negatively regulated by as yet undefined inhibitory receptors.

Identification of HLA-B27-restricted cytotoxic T lymphocyte epitope from carcinoembryonic antigen

Characterization of epitopes recognized by cytotoxic T lymphocytes (CTLs) in the sequence of tumor antigens is an important step in the development of tumor therapies. Because carcinoembryonic antigen (CEA) is a protein expressed in a high number of epithelial tumors, it is an interesting target to study. We screened for the presence of HLA-B27-restricted CTL epitopes from CEA by studying the binding to HLA-B27 of 31 synthetic peptides predicted to bind to this molecule. This afforded 16 peptides with moderate or high binding affinity. Immunization of HLA-B27 transgenic mice with the best binder peptides yielded 4 immunogenic peptides: CEA(9-17), CEA(9-18), CEA(138-146) and CEA(360-369). However, splenocytes from mice immunized with a vaccinia virus-expressing CEA recognized only CEA(9-18). These CTLs were of the CD8(+) phenotype, which upon stimulation with peptide specifically produced IFN-gamma. Moreover, they did not cross-react against peptides of region 9-18 from proteins of the CEA family. Our results show that CEA(9-18) may induce specific CTL responses against CEA.

Linkage disequilibria between HLA-B, C1_4_1, MICA and MICB

The polymorphisms of MICA exon 5 (5 alleles), MICB intron 1 (13 alleles), C1_4_1 (6 alleles), HLA-B (29 alleles) and HLA-A (15 alleles) were investigated in a healthy German population. Sequencing was performed for the MICB alleles CA14, CA15, CA17, CA23 and CA26 isolated from different cell lines. Variation to the published sequence was observed for CA14, CA15 and for CA17. At the C1_4_1 locus a new allele (CAAA)9 was identified and confirmed by sequencing. Linkage disequilibria were investigated for two-point- and three-point-haplotypes. Although the average relative delta value correlates loosely with the physical distance from HLA-B to MICB: HLA-B-C1_4_1>HLA-B-MICA>HLA-B-MICB, there are several exceptions to this rule. Analyzing three-point-haplotypes for the segment MICB to HLA-A a wide variation of linkage disequilibria for some of the classical HLA-A, B haplotypes has been observed. While the HLA-A1, B8 haplotype displays strong relative delta values over the entire distance from HLA-A to MICB, other haplotypes have linkage disequilibria only in a limited region.

MICA, MICB and C1_4_1 polymorphism in Crohn's disease and ulcerative colitis

MICA and MICB belong to a multicopy gene family located in the major histocompatibility complex (MHC) class I region near the HLA-B gene. They encode for MHC class I molecules, which are induced by stress factors like infection, heat shock or neoplastic transformation and which are mainly expressed on gastrointestinal epithelium. They are recognized by gammadelta T lymphocytes and natural killer (NK) cells. Additionally they are located within a linkage region on chromosome 6p around HLA-B and TNFalpha. Thus the polymorphic MICA and MICB genes are excellent candidate genes for providing the genetic background of inflammatory bowel disease. A strong association of allele A6 of the MICA exon 5 trinucleotide microsatellite polymorphism with ulcerative colitis has been found in Japanese patients. Therefore, we have analysed the MICA exon 5 polymorphism, the MICB intron 1 dinucleotide polymorphism and in addition the tetranucleotide polymorphism C1_4_1, which is located between the MICA gene and the HLA-B gene, in patients of Caucasoid origin with Crohn's disease (n=94) and ulcerative colitis (n=94). In this study we could not find any associations of particular alleles of the MICA, MICB and C1_4_1 polymorphisms with Crohn's disease or ulcerative colitis. We could also not discover any associations of specific two-point or three-point haplotypes with these diseases. Thus it is unlikely that the MICA and MICB genes are involved in causing susceptibility for inflammatory bowel disease, although it cannot be excluded that a weak association could be identified in a larger patient sample.

Implications of HLA-E allele expression and different HLA-E ligand diversity for the regulation of NK cells

The interaction of HLA-E with CD94/NKG2A is dependant on the binding of HLA class I signal sequence derived peptides to HLA-E. In the caucasoid population two HLA-E alleles are observed at equal frequencies. Here we study the functional differences between the two HLA-E molecules with regard to cell surface expression, peptide binding, and potential to inhibit lytic activity of a CD94/NKG2A(+) NK cell line. In contrast to the HLA-E(R) allele, the HLA-E(G) allele shows considerable cell surface expression even in the absence of endogenous HLA class I signal sequence derived HLA-E ligands. Eighteen HLA-E allele/HLA-E ligand combinations were analyzed. No correlation between cell surface expression of HLA-E and NK cell inhibition was observed. The peptides present in the signal sequences of HLA-B15, -Cw0402, and -Cw7 bound to both HLA-E alleles but did not lead to an inhibition of NK cell lysis. In our experimental system the peptides A2 and G were not effective with regard to NK cell inhibition when bound to the HLA-E(R) allele. These results may be of functional significance particularly in the placenta where the only HLA-E ligands are derived from HLA-G and -C.

Muscle fibers in inflammatory myopathies and cultured myoblasts express the nonclassical major histocompatibility antigen HLA-G

We demonstrate that HLA-G, a nonclassical major histocompatibility complex class I antigen, is expressed in muscle fibers in various inflammatory myopathies. Further, interferon-gamma induces surface expression and upregulation of mRNA transcripts corresponding to different isoforms of HLA-G in myoblasts cultured from control subjects and patients. HLA-G may have important immunological functions in inflammatory myopathies and other local immune reactions as they occur during vaccination, myoblast transplantation, and gene therapy.

Recombinant versus natural human 111In-beta2-microglobulin for scintigraphic detection of Abeta2m amyloid in dialysis patients

BACKGROUND

We previously introduced scintigraphy with 131I-labeled beta2-microglobulin (beta2m), purified from uremic hemofiltrate, that is, "natural" beta2m, to specifically detect beta2m-associated amyloidosis (Abeta2m) in hemodialysis (HD) patients.

METHODS

To improve the safety and resolution of the scan, we covalently bound the chelator diethylenetriaminepentaacetic acid to natural beta2m to allow radiolabeling with 111In. In a second step, we generated and evaluated the usage of recombinant human beta2m (rhbeta2m) for scintigraphy.

RESULTS

Using natural 111In-labeled beta2m, eight patients on HD for 0 to 17 years, without evidence of Abeta2m, were scanned. Whole-body scintigraphy at 48 to 72 hours postinjection revealed no significant tracer accumulation over joint regions. In contrast, nine patients on HD for 10 to 21 years with clinical, radiological, or histologic (N = 4) evidence of Abeta2m showed selective tracer uptake over various joint regions. Tracer accumulation in visceral organs, which could not be related to tracer elimination or metabolism, was not detected. Compared with the previous 131I beta2m scan, scintigraphy with 111In-labeled beta2m offered highly improved image contrast, increased sensitivity, and a 50 to 70% reduction of the radiation exposure. Scanning with 111In-labeled recombinant human beta2m was performed in six patients: No significant tracer accumulation was observed over joint regions in two patients on short-term HD without evidence of Abeta2m; in contrast, local tracer accumulations similar to those observed with natural beta2m could be demonstrated in four long-term (10 to 27 years) HD patients with clinical, radiological, and histologic (N = 1) evidence of Abeta2m.

CONCLUSION

Scintigraphy for Abeta2m with 111In-labeled rhbeta2m provides a homogenous and safe recombinant protein source and leads to enhanced sensitivity and lower radiation exposure.

Cutting edge: the human cytomegalovirus UL40 gene product contains a ligand for HLA-E and prevents NK cell-mediated lysis

Human CMV has evolved multiple strategies to interfere with immune recognition of the host. A variety of mechanisms target Ag presentation by MHC class I molecules resulting in a reduced class I cell-surface expression. This down-regulation of class I molecules is expected to trigger NK cytotoxicity, which would have to be counteracted by the virus to establish long-term infection. Here we describe that the human CMV open reading frame UL40 encodes a canonical ligand for HLA-E, identical with the HLA-Cw03 signal sequence-derived peptide. Expression of UL40 in HLA-E-positive target cells conferred resistance to NK cell lysis via the CD94/NKG2A receptor. Generation of the UL40-derived HLA-E ligand was also observed in TAP-deficient cells. The presence of a functional TAP-independent HLA-E ligand in the UL40 signal sequence implicates this viral gene as an important negative regulator of NK activity.

LST1: a gene with extensive alternative splicing and immunomodulatory function

The gene of the leukocyte-specific transcript (LST1) is encoded within the TNF region of the human MHC. The LST1 gene is constitutively expressed in leukocytes and dendritic cells, and it is characterized by extensive alternative splicing. We identified 7 different LST1 splice variants in PBMC; thus, 14 LST1 splice variants (LST1/A-LST1/N) have been detected in various cell types. These isoforms code for transmembrane as well as soluble LST1 proteins characterized by two alternative open reading frames at their 3' end. We demonstrate the presence of the transmembrane variant LST1/C on the cell surface of the monocytic cell lines U937 and THP1. Recombinant expression of LST1/C permitted its profound inhibitory effect on lymphocyte proliferation to be observed. In contrast, the alternative transmembrane variant LST1/A, the extracellular domain of which shows no amino acid sequence homology to LST1/C exerted a weaker but similar inhibitory effect on PBMC. These data demonstrate the protein expression of LST1 on the cell surface of mononuclear cells, and they show an inhibitory effect on lymphocyte proliferation of two LST1 proteins although they have only a very short amino acid homology.

Association of beta(2)-adrenoreceptor variants with bronchial hyperresponsiveness

Because of its involvement in the regulation of airway tone, the beta(2)-adrenoreceptor is considered a candidate for bronchial hyperresponsiveness (BHR) associated with asthma. This notion is supported by several reports that have implicated the chromosomal region 5q31-q33 harboring the gene for the beta(2)-adrenoreceptor in the genetics of asthma and related phenotypes. We performed a population-based association study focusing on BHR as a qualitative trait and omitting other asthma-related phenotypes. From a German population sample of 1,150 individuals we extracted all 152 bronchohyperreactive probands, who were compared with 295 bronchonormoreactive control subjects. All individuals were genotyped for three single nucleotide polymorphisms of the beta(2)-adrenoreceptor gene resulting in variants at the amino acid positions 16, 27, and 164. The genotyping protocol used allowed the determination of haplotypes of these polymorphisms. Whereas no individual polymorphism was associated with BHR, the Gly16/Gln27/Th164 haplotype was significantly underrepresented in the case group indicating a protective effect of this haplotype with regard to BHR. Upon reanalysis by sex a significant association persisted only for female probands.

Production of recombinant human beta2-microglobulin for scintigraphic diagnosis of amyloidosis in uremia and hemodialysis

Amyloid of beta2-microglobulin (beta2m) origin can be diagnosed using 131I-radiolabelled-beta2m scintigraphy in patients with uremia and hemodialysis treatment. As the tracer beta2m is isolated from another patient, it carries the common risks, including viral infections such as Hepatitis B, C and HIV, which are associated with human plasma products. In order to exclude these risks we have produced recombinant human beta2m (rhbeta2m) in Escherichia coli. The expression vector pASK40DeltaLbeta2m(His)5 contains a C-terminal (His)5-tag for purification via immobilized metal ion affinity chromatography (IMAC). Size exclusion chromatography on a Superose 12 column represents the second step of purification. The isolated rhbeta2mH5 reacted in an immunochemically identical manner to native human beta2m, and showed a single band of approximately 11.8 kDa in Western blot analysis and revealed a single spot in two-dimensional gel electrophoresis. Mass spectrometry analysis revealed a single peak at the expected molecular mass of 12 415.8 Da. Uniformity was further proven by crystallization and N-terminal amino-acid sequence analysis. The rhbeta2mH5 protein was then produced under conditions that allow the intravenous use in humans. Intraveneously applied indium-111-labelled rhbeta2mH5 was monitored in hemodialysed patients with and without known beta2m-amyloidosis. The tracer was localized specifically to particular areas known to contain amyloid. Thus, this rhbeta2mH5 preparation is suitable for detecting amyloid-containing organs of the beta2m-class in vivo and fulfils the requirements of a tracer for common use. Finally, the use of indium-111 instead of iodine-131 has reduced the radioactive load and resulted in higher resolution.

Cell surface detection of HLA-E gene products with a specific monoclonal antibody

An HLA-E-specific monoclonal antibody (mAb) was obtained by immunization of human beta2-microglobulin transgenic mice (M-TGM) with spleen cells from double transgenic mice expressing HLA-E molecules (EM-TGM). This mAb, designated V16, specifically recognizes in flow cytometry analysis the HLA-E expressing mouse cells, whereas it does not bind to mouse cells expressing various HLA class I molecules (HLA-A2, -A3, -A11, -A26, A29, -B7, -B27, -Cw3, -Cw7, and HLA-G). V16 mAb binds efficiently to human EBV-infected B lymphocytes, PHA blasts and PBL, thus establishing the surface expression of HLA-E in vivo on these cells.