Cell attachment, collagen binding, and receptor analysis on bovine articular chondrocytes

The purpose of this study was to investigate collagen receptors on primary bovine articular chondrocytes from full-thickness and different layers of bovine articular cartilage. Cytometric studies with antibodies showed that approximately 56% of the chondrocytes from the superficial layer and 29% of the chondrocytes from the deep layer bound anti-annexin V. A similar tendency was found for alpha5 and beta1 integrin antibodies. Flow cytometric analysis initially detected annexin V on chondrocytes following isolation; the level of detection subsequently decreased by 24 hours, whereas that of alpha5 and beta1 integrins increased. Treatment of chondrocytes with collagenase at 24 hours restored the initially high epitope recognition of annexin V, indicating masking of annexin V by newly formed collagen matrix. There was little effect on detection levels for beta1 integrin. Contrary to the specific matrix receptor expression, chondrocytes from superficial and deep layers differed little in attachment to immobilized types I and II collagens. However, the attachment was more effectively inhibited with anti-annexin V than with integrin antibodies. Competition studies with preparations of soluble collagens revealed a preferential binding of bovine type-II collagen compared with bovine type-I collagen. Anti-annexin V antibodies inhibited binding of type-II collagen more effectively than anti-alpha5 or anti-beta1 integrin antibodies. Evidently, under the in vitro conditions of this study, annexin V is the quantitatively predominant type-II collagen receptor on bovine articular chondrocytes. This opens a discussion of the possibly dualistic metabolic/mechanical annexin V-integrin receptor elements.

DMBT1 encodes a protein involved in the immune defense and in epithelial differentiation and is highly unstable in cancer

The gene deleted in malignant brain tumors 1 (DMBT1) has been proposed as a candidate tumor suppressor for brain, gastrointestinal, and lung cancer. It codes for a protein of unknown function belonging to the superfamily of scavenger receptor cysteine-rich proteins. We aimed at getting insights into the functions of DMBT1 by expression analyses and studies with a monoclonal antibody against the protein. The DMBT1 mRNA is expressed throughout the immune system, and Western blot studies demonstrated that isoforms of DMBT1 are identical to the collectin-binding protein gp-340, a glycoprotein that is involved in the respiratory immune defense. Immunohistochemical analyses revealed that DMBT1 is produced by both tumor-associated macrophages and tumor cells and that it is deregulated in glioblastoma multiforme in comparison to normal brain tissue. Our data further suggest that the proteins CRP-ductin and hensin, both of which have been implicated in epithelial differentiation, are the DMBT1 orthologs in mice and rabbits, respectively. These findings and the spatial and temporal distribution of DMBT1 in fetal and adult epithelia suggest that DMBT1 further plays a role in epithelial development. Rearrangements of DMBT1 were found in 16 of 18 tumor cell lines, and hemizygous deletions were observed in a subset of normal individuals, indicating that the alterations in tumors may be a result of both pre-existing deletions uncovered by a loss of heterozygosity and secondary changes acquired during tumorigenesis. Thus, DMBT1 is a gene that is highly unstable in cancer and encodes for a protein with at least two different functions, one in the immune defense and a second one in epithelial differentiation.

Detection and molecular mass determination of an HIV replication-enhancing female genital tract factor using a blot bioassay

We previously reported that cervicovaginal lavages (CVL) contain a factor that enhances the replication of human immunodeficiency virus (HIV) by increasing virus transcription in T cells and monocytoid cells. This factor was named the HIV-inducing factor (HIF). To determine the molecular mass of HIF, we adapted a blot technique that involves nonreducing SDS-PAGE of CVL samples and electrophoretic transfer onto nitrocellulose paper followed by incubation of paper slices with HIV-infected monocytoid U1 cells. The slices with HIF bioactivity were detected by increased HIV production and measured by an HIV core protein (p24) ELISA. We refer to this technique as the "BioBlot" assay. The BioBlot assay successfully detected bioactivity of HIF anchored onto nitrocellulose and determined that HIF has a molecular mass of about 14 kDa. Paper slices with HIF-negative CVL samples as well as nitrocellulose paper samples without CVL did not enhance HIV production. This finding suggested that SDS-PAGE and nitrocellulose binding do not functionally alter the bioactive domain(s) of HIF structure. In addition to the detection of HIF bioactivity anchored to nitrocellulose and HIF molecular mass determination, the BioBlot technique offers an alternative, rapid method for other applications. These include the study of receptor-ligand interactions of mucosal proteins, direct bioactivity testing and molecular mass determination of secretory substances.

Human articular chondrocytes express osteogenic protein-1

This study demonstrates for the first time that human articular chondrocytes express osteogenic protein-1 (OP-1). OP-1 was originally purified from bone matrix and was shown to induce cartilage and bone formation. Both OP-1 protein and message were present in human normal and osteoarthritic (OA) cartilages. OP-1 mRNA was upregulated in OA cartilage compared with normal adult tissues. However, the level of mature OP-1 protein in the same OA tissues was downregulated, whereas the pro-OP-1 remained high. Moreover, these two forms of OP-1 were localized in an inverted manner. Mature OP-1 was primarily detected in the superficial layer, whereas the pro-form was mostly in the deep layer of cartilage. The presence of pro- and mature OP-1 in extracts of normal and OA cartilages was confirmed by Western blotting. These findings imply that articular chondrocytes continue to express and synthesize OP-1 throughout adulthood. The observed patterns of the distribution of pro- and mature OP-1 also suggest differences in the processing of this molecule by normal and OA chondrocytes and by the cells in the superficial and deep layers. Distinct distribution of OP-1 and its potential activation in deep zones and regions of cloning in OA cartilages may provide clues to the potential involvement of endogenous OP-1 in repair mechanisms. (J Histochem Cytochem 48:239-250, 2000)

Functional failure of fascia lata allografts

OBJECTIVES

Fascia lata allografts are commonly used in urogynecologic procedures. Functional failure of several grafts has occurred, and such failure has been recognized as a materials problem in 12 patients.

STUDY DESIGN

Twelve patients with failure of an initial urogynecologic procedure performed with irradiated and freeze-dried donor fascia lata grafts underwent reoperation. Portions of the implanted fascia lata grafts could be retrieved in 7 cases. Graft specimens underwent histologic processing followed by hematoxylin and eosin staining.

RESULTS

Histopathologic analyses of the retrieved material demonstrated several ongoing processes in the failed grafts. A few grafts showed areas of ideal remodeling. Most grafts, however, showed areas of disorganized remodeling and areas of graft degeneration. Evidence of immune reaction to the graft was observed in some cases.

CONCLUSION

The high materials failure rate associated with the use of irradiated and freeze-dried donor fascia lata grafts suggests that such tissue should not be used for urogynecologic procedures.

The genomic structure of the DMBT1 gene: evidence for a region with susceptibility to genomic instability

Increasing evidence has accumulated for an involvement of the inactivation of tumour suppressor genes at chromosome 10q in the carcinogenesis of brain tumours, melanomas, and carcinomas of the lung, the prostate, the pancreas, and the endometrium. The gene DMBT1 (Deleted in Malignant Brain Tumours 1) is located at chromosome 10q25.3-q26.1, within one of the putative intervals for tumour suppressor genes. DMBT1 is a member of the scavenger-receptor cysteine-rich (SRCR) superfamily and displays homozygous deletions or lack of expression in glioblastoma multiforme, medulloblastoma, and in gastrointestinal and lung cancers. Based on these properties, DMBT1 has been proposed to be a candidate tumour suppressor gene. We have determined the genomic sequence of DMBT1 to allow analyses of mutations. The gene has at least 54 exons that span a genomic region of about 80 kb. We have identified a putative exon with coding potential for a transmembrane domain. Our data further suggest that alternative splicing gives rise to isoforms of DMBT1 with a differential utilization of SRCR domains and SRCR interspersed domains. The major part of the gene harbours locus specific repeats. These repeats may point to the DMBT1 locus as a region susceptible to chromosomal instability.

Failure of allograft suburethral slings

OBJECTIVES

To report our experience of using freeze-dried irradiated fascia lata allografts for suburethral sling procedures.

PATIENTS AND METHODS

Between December 1996 and September 1998, 35 patients (mean age 60.25 years, range 37-79) underwent suburethral sling placement with fascia allograft. These patients were reviewed, with the findings at the time of any surgical re-exploration. Eleven (31%) had undergone prior surgery for genuine stress incontinence and 32 (91%) had a preoperative diagnosis of intrinsic sphincter deficiency.

RESULTS

On re-operation for persistent or recurrent stress incontinence, the allograft was present but grossly degenerated in two (6%) patients and completely absent in five (14%) patients. Histology of a retrieved graft fragment showed both fibroblast proliferation and degeneration within the graft.

CONCLUSION

The use of freeze-dried, irradiated fascia lata for suburethral sling procedures was associated with a material failure rate of >/=20%. We caution against its use in this setting.

Cloning of gp-340, a putative opsonin receptor for lung surfactant protein D

Surfactant protein D (SP-D) is an oligomeric C type lectin that promotes phagocytosis by binding to microbial surface carbohydrates. A 340-kDa glycoprotein (gp-340) has been shown to bind SP-D in the presence of calcium but does so independently of carbohydrate recognition. This protein exists both in a soluble form and in association with the membranes of alveolar macrophages. The primary structure of gp-340 has been established by molecular cloning, which yielded a 7,686-bp cDNA sequence encoding a polypeptide chain of 2, 413 amino acids. The domain organization features 13 scavenger receptor cysteine-rich (SRCR) domains, each separated by an SRCR-interspersed domain, except for SRCRs 4 and 5, which are contiguous. The 13 SRCR domains are followed by two C1r/C1s Uegf Bmp1 domains separated by a 14th SRCR domain and a zona pellucida domain. gp-340 seems to be an alternative spliced form of DMBT1. Reverse transcription-PCR analysis showed that the main sites of synthesis of gp-340 are lung, trachea, salivary gland, small intestine, and stomach. Immunohistochemistry revealed strong staining for gp-340 in alveolar and other tissue macrophages. Immunostaining of the macrophage membrane was either uniform or focal in a way that suggested capping, whereas other macrophages showed strong intracellular staining within the phagosome/phagolysosome compartments. In some macrophages, SP-D and gp-340 were located in the same cellular compartment. Immunoreactive gp-340 was also found in epithelial cells of the small intestine and in the ducts of salivary glands. The distribution of gp-340 in macrophages is compatible with a role as an opsonin receptor for SP-D.

Expression of anchorin CII (cartilage annexin V) in human young, normal adult, and osteoarthritic cartilage

In its tissue-specific function as a collagen receptor of chondrocytes, cartilage annexin V (anchorin CII) occupies a key position in the organization of the cell-extracellular matrix (ECM) junction for the tissue. The general role of annexin V (Anx V) in other tissues suggests involvement in cellular secretory processes and in regulation of apoptosis. Immunohistochemical analysis of Anx V in growth plate cartilage, confirmed by in situ hybridization, suggests that Anx V is prominently expressed and forms a major constituent of growth plate chondrocytes. Anx V epitopes are also located in the pericellular matrix of hypertrophic cartilage. In adult articular cartilage the expression is downregulated, with the highest levels of immunostaining found in the upper third of the articular cartilage layers and almost no antigen found in the deep layers. Osteoarthritic (OA) cartilage is characterized by a significant upregulation of message and protein throughout the entire depth of the tissue, an accumulation of cytoplasmic annexin V epitopes, and a release of epitopes into the pericellular and interterritorial matrix, in part co-localized with granular structures. Therefore, Anx V expression and tissue distribution may serve as a histological marker for metabolic alterations and for changes in the cellular phenotype associated with OA.

Molecular analysis of childhood primitive neuroectodermal tumors defines markers associated with poor outcome

PURPOSE

The diagnostic and prognostic significance of well-defined molecular markers was investigated in childhood primitive neuroectodermal tumors (PNET).

MATERIALS AND METHODS

Using microsatellite analysis, Southern blot analysis, and fluorescence in situ hybridization (FISH), 30 primary tumors and six CSF metastasis specimens were analyzed for loss of heterozygosity (LOH) of chromosomes 1q31, 6q, 9q22, 10q, 11, 16q22, and 17p13.1 and/or high-level amplification of the c-myc gene. Experimental data were compared with clinical stage and outcome.

RESULTS

LOH of chromosome 17p13.1 was found most frequently (14 of 30 tumors, six of six CSF metastasis specimens); LOH of chromosomes 10q, 16q22, 11, 6, 9q22, and 1q31 was observed in 20.6%, 20%, 14.3%, 12%, 10%, and 0%, respectively. Eight of 32 tumors and CSF specimens showed amplification of c-myc. All tumors with amplification of c-myc were resistant to therapy and had a fatal outcome (mean survival time, 9.3 months). Tumors that displayed LOH of chromosome 17p were associated with metastatic disease. The prognosis of these tumors was worse only when associated with amplification of c-myc. Three of three patients with LOH of 9q22 relapsed.

CONCLUSION

In our study, amplification of c-myc was a poor-prognosis marker in PNET. LOH of chromosome 17p was associated with metastatic disease. Molecular analysis of primary tumors using these markers may be useful for stratification of children with PNET in future prospective studies. The other aberrations investigated were not of significant prognostic value, but may provide an entry point for future large-scale molecular studies.

Culture of chondrocytes in alginate gel: variations in conditions of gelation influence the structure of the alginate gel, and the arrangement and morphology of proliferating chondrocytes

Sodium alginate, which gels in the presence of calcium ions, is commonly used for culture of anchorage-independent cells, such as chondrocytes. Normally, the gel appears microscopically homogeneous but, depending on the conditions of gelation, it may contain a varying number of small channels that extend inward from the surface. We have examined the influence of these channels on the morphology of cultured chondrocytes entrapped in alginate beads. Growth-plate or articular chondrocytes cultured in alginate normally proliferate and form rounded cell clusters but, in alginate beads containing numerous channels, many chondrocytes become aligned and form columns similar to those in the growth plate in vivo. As the pattern of cellular growth and morphology in alginate is profoundly influenced by the presence of channels in the gel, further studies were conducted to determine what specific conditions of gelation affect their formation. The channels are especially numerous when both the alginate and the gelling solutions lack sodium ions or other monovalent cations. The channels are cavities in the gel formed by particulate blocking of the rapid diffusion of calcium ions from the gelling solution into the boundary of the calcium alginate solution, and hence they extend inward from cells at the surface of the alginate gel. An understanding of the conditions under which these channels develop makes it possible either to avoid their formation or, alternatively, to enhance the number of channels in order to encourage proliferating cells to grow in radial columns, rather than in a less organized pattern characteristic of most culture systems.

Effects of recombinant human osteogenic protein 1 on the production of proteoglycan, prostaglandin E2, and interleukin-1 receptor antagonist by human articular chondrocytes cultured in the presence of interleukin-1beta

OBJECTIVE

Recombinant human osteogenic protein 1 (OP-1) is an effective stimulator of human cartilage 35S-proteoglycan synthesis. The present study was conducted to determine whether stimulation of human articular chondrocytes with OP-1 can help overcome interleukin-1beta (IL-1beta)-induced suppression of 35S-proteoglycan synthesis.

METHODS

Human articular chondrocytes in alginate beads were maintained for 3 days in the absence (control) or presence of IL-1beta at 0.1-100 pg/ml with or without OP-1 at 50 ng/ml, in medium containing 10% fetal bovine serum (FBS). Incorporation of 35S-sulfate into proteoglycans was quantified during the last 4 hours of culture and reported as counts per minute per microg DNA. Release of interleukin-1 receptor antagonist (IL-1Ra) and prostaglandin E2 into the medium was monitored by immunoassay.

RESULTS

IL-1beta at 10 pg/ml caused a 60% decrease in 35S-proteoglycan synthesis. This could be blocked by including 500 ng/ml IL-1Ra in the medium. The presence of 50 ng/ml OP-1 in the IL-1beta-containing medium was effective in restoring 35S-proteoglycan synthesis to the level of that found in cultures not treated with IL-1beta. The restorative effects of OP-1 and IL-1Ra were cumulative. The rate of release of prostaglandin E2 and IL-1Ra into the medium was not affected by the presence of OP-1.

CONCLUSION

Treatment of human articular chondrocytes with OP-1 cultured in the presence of FBS is effective in overcoming the down-regulation of proteoglycan synthesis induced by low doses of IL-1beta.

DMBT1, a new member of the SRCR superfamily, on chromosome 10q25.3-26.1 is deleted in malignant brain tumours

Loss of sequences from human chromosome 10q has been associated with the progression of human cancer. Medulloblastoma and glioblastoma multiforme are the most common malignant brain tumours in children and adults, respectively. In glioblastoma multiforme, the most aggressive form, 80% of the tumours show loss of 10q. We have used representational difference analysis to identify a homozygous deletion at 10q25.3-26.1 in a medulloblastoma cell line and have cloned a novel gene, DMBT1, spanning this deletion. DMBT1 shows homology to the scavenger receptor cysteine-rich (SRCR) superfamily. Intragenic homozygous deletions has been detected in 2/20 medulloblastomas and in 9/39 glioblastomas multiformes. Lack of DMBT1 expression has been demonstrated in 4/5 brain-tumour cell lines. We suggest that DMBT1 is a putative tumour-suppressor gene implicated in the carcinogenesis of medulloblastoma and glibolastoma multiforme.

Annexin V interactions with collagen

Annexin V was originally identified as a collagen-binding protein called anchorin CII and was isolated from chondrocyte membranes by affinity chromatography on native type II collagen. The binding of annexin V to native collagen type II is stable at physiological ionic strength when annexin V is reconstituted in liposomes. The binding to native collagen types II and X, and to some extent to type I as well, was confirmed using recombinant annexin V. A physiological role for annexin V interactions with extracellular collagen is consistent with the localization of annexin V on the outer cell surface of chondrocytes, microvilli of hypertrophic chondrocytes, fibroblasts and osteoblasts. A breakthrough in our understanding of the function of annexin V was made with the discovery of its calcium channel activity. At least one of several putative functions of annexin V became obvious from studies on matrix vesicles derived from calcifying cartilage. It was found that calcium uptake by matrix vesicles depend on collagen type II and type X binding to annexin V in the vesicles and was lost when collagens were digested with collagenase: calcium influx was reconstituted after adding back native collagen II or V. These findings indicate that annexin V plays a major role in matrix vesicle-initiated cartilage calcification as a collagen-regulated calcium channel.

Annexins: what are they good for?

Annexins comprise a unique family of calcium- and phospholipid-binding proteins. At least one of the twenty members thus far described from this family can be found expressed in nearly every eukaryotic cell type. As common as these proteins may be, no one clear function for all has been established. Historically, individual members of this family have been given various names describing their ability to associate with a host of intra- and extracellular proteins and with cellular lipid membranes. The collection of reviews in this issue of CMLS represents an effort to offer a coordinated view of the research activities in the field and to extract structural and functional commonalities.

Absence of cell-surface annexin V is accompanied by defective collagen matrix binding in the Swarm rat chondrosarcoma

Annexin V has been characterized as a major collagen type II binding cell-surface component of normal chondrocytes and is also called anchorin CII in chondrogenic populations. Herein we present evidence that in vitro cultured Swarm rat chondrosarcoma cells are not capable of binding collagen type II in significant quantities to their surfaces, as compared to normal rat chondrocytes. This finding coincides with a deficiency of annexin V on the surface of these cells. A small quantity of an intracellular polypeptide could be detected which is immunologically cross-reactive with annexin V but displayed a mobility in SDS-PAGE of less than 34 kD compared to the M(r) 36 kD of intact rat annexin V. By immunohistochemistry the protein could be localized in the cytoplasm of in vitro and in vivo grown tumor cells. By reverse transcription-polymerase chain reaction and Northern blot analysis, a regular-sized mRNA for annexin V could be detected in the chondrosarcoma cells that is expressed in only slightly lower quantities than in normal chondrocytes. Taken together, the data suggest a modified processing or turnover for annexin V in the chondrosarcoma excluding it from being a functionally active collagen type II binding protein. The findings support the hypothesis of cell-surface annexin V as a key component for the formation of the pericellular matrix of chondrocytes.

Analysis of 3H-proline-labeled protein by rapid filtration in multiwell plates for the study of collagen metabolism

Quantitative and qualitative analysis of cell cultures labeled with 3H-proline for monitoring collagen synthesis is time-consuming and occasionally generates large quantities of radioactive waste. This present work describes the application of a microwell filtration system for the analysis of collagen metabolism in chondrocytes. It is based on trichloroacetic acid (TCA) precipitation of 3H-proline-labeled proteins onto polyvinylidene difluoride membranes fitted in a 96-well plate and subsequent analysis of precipitated proteins by liquid scintillation counting, amino acid analysis and sodium dodecyl sulfate (SDS) gel electrophoresis. This method allows for the initial processing of 96 samples within 2 h, has high sensitivity and accuracy (linearity > or = 200 cpm/sample) for quantitative measurements and a capacity of up to 10 micrograms collagen/microwell. The ratio of the radioactive protein collected by this filtration assay compared to that collected by molecular sieve chromatography on Sephadex G-25 was linear over a broad range, indicating full compatibility of data and a high reproducibility for both assay systems. The quality of protein separation by SDS-polyacrylamide gel electrophoresis (PAGE) from samples obtained by the filtration assay and by dialysis was virtually identical. These features make the assay particularly suited for pulse-chase experiments and for monitoring protein degradation.

[Do calcium and zinc ions influence matrix molecule synthesis of chondrocytes?]

The experiments described here tested the effect of various calcium (Ca) and Zinc (Zn) concentrations on cell proliferation and matrix molecule synthesis of fetal and adult bovine chondrocytes in monolayer cultures. Levels of Ca < 0.2 mM in a culture medium or the addition of Zn (0.1-50 microM) selectively promoted the production of collagen but did not affect significantly synthesis of proteoglycans. No change in proliferation of fetal and adult chondrocytes could be observed. In contrast 10 mM Ca promoted the hypertrophic differentiation of chondrocytes (e.g. expression of collagen type X). The results are related to calcium channel configurations in chondrocytes in the discussion.

Collagen and proteoglycan production by bovine fetal and adult chondrocytes under low levels of calcium and zinc ions

The experiments described herein tested the effects of CaCl2 and ZnCl2, added at various concentrations in the culture medium, upon the synthesis of collagen and proteoglycan by adult and fetal (articular, epiphyseal and hypertrophic) bovine chondrocytes maintained in high density multilayer cultures. CaCl2 concentrations below 0.5 mM or the addition of 1-50 microM ZnCl2 to the medium selectively promoted the production of collagen by all four populations of chondrocytes but had no effect on fibroblasts. Further, these changes had no statistically significant effect on the incorporation of 35S-sulfate into macromolecules or on the synthesis of gelatinase A, measured by gelatin zymography. The addition of CaCl2 and ZnCl2 at these concentrations did not result in a change in the relative proportion of non-crosslinked 3H-collagen molecules (synthesized in the presence of beta-aminopropionitrile) partitioning in the cell layer and medium compartments, and did not appreciably alter the pattern of collagens synthesized by any of the cell populations. The hypertrophic cells synthesized high levels of collagen type X in the presence as well as absence of exogenously added cations. However, CaCl2 at 10 mM caused a marked upregulation of collagen type X synthesis by a preparation of chondrocytes derived from the entire growth plate, consistent with the view that calcium at that concentration stimulated the differentiation of some of the cells into hypertrophic chondrocytes.

Structural and functional comparison of anchorin CII (cartilage annexin V) and muscle annexin V

Annexin V has been isolated from chicken muscle and cartilage either by EDTA extraction or by plasma membrane purification and solubilization with detergent to obtain the hydrophilic and hydrophobic variants. The hydrophobic variant of the cartilage annexin V associated with phosphatidylserine-containing liposomes in a Ca(2+)-independent manner, whereas the EDTA-extracted molecule required Ca2+ for association with the liposomes. The collagen-binding assay used is based on the principle of a cell attachment assay using mildly pepsinized collagen type II or intact collagen type I as the solid-phase substrate. Soluble intact collagen type I or II was added as competitive inhibitor. The lipophilic and the EDTA-extracted anchorins CII from cartilage were inhibited to the same extent by collagen type II on pepsinized collagen type II as the solid-phase substrate. The EDTA-extracted muscle annexin V exhibited a fivefold lower affinity to collagen type II than its counterpart from cartilage. Peptide mapping studies and amino acid sequencing of selected peptides from the hydrophobic cartilage annexin V and the hydrophilic cartilage and muscle annexin V revealed 100% identity to the established chicken annexin V protein sequence in the corresponding amino acids 7-29 and 118-126. These results indicate that annexin V may occur in multiple pools within one cell type and/or tissue and that its biological function may depend on the subcellular distribution as well as the microenvironment in the tissue.

Isolation and characterization of a cartilage-specific membrane antigen (CH65): comparison with cytokeratins and heat-shock proteins

We report the isolation and characterization of a 65,000 MW chondrocyte autoantigen (CH65) which may be involved in rheumatoid arthritis. This chondrocyte-specific antigen reacted with sera from patients with rheumatoid arthritis (RA). CH65 did not cross-react with a polyclonal antibody raised against microbial heat-shock protein (hsp) 65, anti-human hsp 65 monoclonal antibodies (mAb) (LK1 and LK2), anti-microbial hsp 65 mAb (IA10, IIC8 and WTB-78H1) and anti-cytokeratin 8, 18, 19 mAb (NCL5D3MAb). CH65 could be purified from chicken chondrocyte membranes by ammonium sulphate precipitation and a novel electro-gel-filtration method. The amino acid analysis yielded an unusually high degree of glycine, serine and asparagine residues. The internal amino acid sequence obtained by tryptic digestion revealed homologies with the cytokeratin family. Despite these homologies, CH65 lacked immunological cross-reactivity with commercial anti-cytokeratin antibodies. Mice mAb generated against the purified CH65 (C6) were used to identify the protein as a tissue-specific constitutive protein membrane from chondrocytes. Sera from patients with RA cross-reacted with purified CH65. The stress or heat-shock protein (hsp 65), implicated in the development of experimental and clinical arthritis, showed no immunological cross-reactivity with CH65 in Western blots. These findings suggest that CH65 may represent an interesting cartilage-specific new antigen in RA. The availability of this antigen in purified form and specific mAb may offer useful tools in arthritis research.

A constitutive 65 kDa chondrocyte protein as a target antigen in adjuvant arthritis in Lewis rats

The autoantigen in adjuvant arthritis in Lewis rats is still unknown despite the knowledge that the 65 kDa mycobacterial heat-shock protein (hsp) is involved in the disease process. T cells and antibodies obtained from rats with adjuvant arthritis respond to chondrocyte membrane antigen(s). In Western blots a 65 kDa chondrocyte membrane protein (CH65) is stained by sera from arthritic rats. In addition, spleen cells from rats with adjuvant arthritis proliferate in vitro to chondrocyte membranes and CH65 as antigens. Furthermore, pretreatment of rats with CH65 or mycobacterial hsp65 but not human hsp60, induces a significant retardation of the onset of adjuvant arthritis in Lewis rats. The data suggest that CH65 is a potential autoantigen involved in the pathogenesis of adjuvant arthritis in Lewis rats.

Triplet repeat sequences in human DNA can be detected by hybridization to a synthetic (5'-CGG-3')17 oligodeoxyribonucleotide

The seemingly autonomous amplification of naturally occurring triplet repeat sequences in the human genome has been implicated in the causation of human genetic disease, such as the fragile X (Martin-Bell) syndrome, myotonic dystrophy (Curshmann-Steinert), spinal and bulbar muscular atrophy (Kennedy's disease) and Huntington's disease. The molecular mechanisms underlying these triplet amplifications are still unknown. We demonstrate here that a synthetic (CGG)17 oligodeoxyribonucleotide can be utilized as hybridization probe to visualize some of the triplet repeats in the human genome. This technique may help in studies aimed at the elucidation of the amplification mechanism.

Preferential cellular and humoral immune reactivities to native and denatured collagen types IX and XI in a patient with fatal relapsing polychondritis

We describe a patient with histologically confirmed relapsing polychondritis, an episodic systemic disorder. Although the etiology is unknown and its pathogenesis is incompletely understood, there is evidence strongly suggesting immunologically mediated mechanisms. Enzyme linked immunosorbent assays, immunoblotting and cellular immune responses using lymphocyte proliferation assays showed strong parallel humoral and cellular immune reactivities against collagens type IX and XI. There was also a considerable response to collagen type II which, however, was less pronounced compared to collagen type IX and was directed to native epitopes. Our findings demonstrate a highly distinct immune response to minor matrix collagens in a destructive cartilage disease and thus strongly argue against nonspecific anticollagen immune reactions simply representing epiphenomena resulting from cartilage damage.

Characterization of macrophage proteins bearing the functional leukotriene D4-binding site of an anti-cysteinylleukotriene monoclonal antibody

Protein conformations of the putative cysteinylleukotriene (LT) receptor of macrophages were characterized using anti-idiotypic IgG (AIAb) against an anti-LT monoclonal Ab (LTmAb). The AIAb nature of two rabbit antisera were demonstrated with titers of up to 1:1000 against F(ab')2 from the LTmAb (in an enzyme-linked immunoassay) which also inhibit LTD4 binding to the LTmAb (in a radioimmunoassay), whereas non-immunized rabbit serum was not reactive. The specific reactivity of Fc-purified AIAb towards LTmAb was measured by two fractions obtained after passage over columns of Sepharose either coupled with LTmAb (fraction A, representing immunoglobulins not absorbed to LTmAb) or coupled with homologous immunoglobins (fraction B, representing immunoglobulins not absorbed to homologous IgG). The difference in immunoreactivity between both fractions showed that fraction B contains AIAb against a LT-recognizing domain of the LTmAb (in enzyme-linked immunoassays coated with LTmAb and homologous IgG) and AIAb against the functional LT-binding site of LTmAb (in radioimmunoassay). Using the antisera, Western-blot analysis with peritoneal cell proteins detected signals at 236, 198, 118, 99, 75, 25 and 18 kDa. Dithiothreitol-reduced proteins were detected at 25 kDa and 18 kDa. In general, this suggested recognition of a 236-kDa oligomeric protein composed of subunits with molecular masses of 25 kDa and 18 kDa, including intramolecular disulfide bridges all bearing an epitope similar to the LTmAb. From these conformations, an overlay assay with [3H]LTD4 favoured a 75-kDa protein. Immunohistochemical analysis demonstrated that the recognized proteins may be located at cell membranes, because (a) in an ELISA, enriched plasma membrane preparations from peritoneal cells showed a threefold increase in reactivity to the AIAb, compared to the original cell homogenate; (b) after Western-blot analysis, the membrane-enriched protein fraction exhibited stronger protein signals than the microsomal fraction and the original cell homogenate; (c) regions of AIAb binding on the surface of cultured mouse peritoneal macrophages were detected by indirect immunofluorescence. Taken together, this study demonstrated AIAb binding to macrophage membrane-associated proteins bearing the LTD4-binding site of LTmAb, which may include identification of the putative LT receptor.