Soluble Fc gamma receptor III in human plasma originates from release by neutrophils.

FcRIII (the CD16-antigen), a low affinity receptor for IgG, is expressed by neutrophils, natural killer lymphocytes, and macrophages. We have developed a sensitive radioimmunoassay to quantify FcRIII. A soluble form of FcRIII was identified in human plasma. Immunoprecipitation of FcRIII from plasma showed that the plasma form of FcRIII has an identical electrophoretic mobility as the FcRIII expressed by neutrophils. Moreover, the plasma form of FcRIII exhibited the same polymorphism as does the neutrophil FcRIII. The neutrophil expresses the phosphatidylinositol-linked form of FcRIII, encoded by the gene FcRIII-1. Because it is not known whether this gene is also active in nonhematopoietic cells, we analyzed patients with an acquired clonal disorder of their hematopoietic cells, paroxysmal nocturnal hemoglobinuria (PNH). PNH patients appeared to have a strongly reduced expression of FcRIII on their neutrophils. The concentration of FcRIII in the plasma of these patients was also reduced, indicating that plasma FcRIII originates from neutrophils. A patient deficient in FcRIII-1 but with a normal expression of FcRIII-2 had no soluble FcRIII in her plasma, also indicating that plasma FcRIII originates from neutrophils. The electrophoretic mobility of the protein backbone of plasma FcRIII and FcRIII released by activated neutrophils was identical, whereas deglycosylated FcRIII obtained from a lysate of neutrophils migrated slower. This indicates that plasma FcRIII originates from activation-induced release by neutrophils. Stimulation of neutrophils or neutrophil cytoplasts (closed membrane vesicles filled with cytoplasm) with low concentrations of FMLP (10(-9)-10(-8) M) or phorbol myristate acetate (1-10 ng/ml) induced a dose-dependent release of FcRIII. The plasma concentration of FcRIII was relatively constant (range 40-280% of the mean). Soluble FcRIII was also detected in inflamed joint fluids of arthritis patients, suggesting that FcRIII is also released by activated neutrophils in vivo.

NH2-terminal globular domain of human platelet glycoprotein Ib alpha has a methionine 145/threonine145 amino acid polymorphism, which is associated with the HPA-2 (Ko) alloantigens.

The glycoprotein (GP) Ib/IX complex, a prominent platelet GP complex, is the primary receptor for vWF. Previously, we have established that an antigenic polymorphism of platelets, the HPA-2 or Ko alloantigen system, is located on the 45-kD amino-terminal globular domain of GPIb alpha. With the polymerase chain reaction, we have amplified two segments of the GPIb alpha gene coding for the first 382 amino acids of two HPA-2a and two HPA-2b homozygous individuals. Nucleotide sequence analysis revealed as the only difference a C-T polymorphism at position 434 of the coding region for the mature protein. This base change results in a substitution of threonine (ACG) in HPA-2a (Kob) to methionine (ATG) in HPA-2b (Koa) at amino acid position 145. The C-T polymorphism is reflected in a difference in restriction enzyme recognition, resulting in an Aha 2-site in the HPA-2b allele and a SfaN1 site in the HPA-2a allele. Restriction fragment length polymorphism analysis of the amplified DNA of 3 HPA-2(a-,b+), 2 HPA-2(a+,b+), and 11 HPA-2(a+,b-) donors showed that these restriction sites were associated with the HPA-2 alleles. DNA-typing for the HPA-2 alloantigen system on genomic DNA obtained from a small number of cells may be applied for determining the genotype of a fetus from an immunized mother or of severely thrombocytopenic patients.

Wegener's granulomatosis autoantibodies identify a novel diisopropylfluorophosphate-binding protein in the lysosomes of normal human neutrophils.

Anti-neutrophil cytoplasmic autoantibodies (ANCA) specifically associated with Wegener's granulomatosis were found to be directed against a saline-soluble glycoprotein triplet that migrates on SDS gels as distinct bands of Mr 29,000, 30,500, and 32,000 and is present in the azurophilic granules. This antigen was specifically recognized by all cytoplasmic-staining (C)-ANCA-positive sera from patients with Wegener's disease. C-ANCA antigen bound [3H]diisopropylfluorophosphate, which indicates that it is a serine protease, but it could clearly be distinguished from the serine proteases elastase and cathepsin G. Stimulation of cytochalasin B-treated neutrophils with FMLP induced release of C-ANCA antigen. This indicates that in vivo C-ANCA might interact with the C-ANCA antigen after its release upon inflammatory stimulation. We further demonstrate that in some perinuclear staining (P-ANCA) patients' sera autoantibodies against other myeloid lysosomal enzymes can be detected, such as antimyeloperoxidase and antielastase. C-ANCA and P-ANCA thus represent a novel class of autoantibodies directed against myeloid lysosomal enzymes. The originally described Wegener-specific C-ANCA show an apparently uniform specificity for the 29,000 serine protease. In contrast, P-ANCA may recognize myeloperoxidase as well as elastase and/or other antigens.

Subsets of CD34+ cells and rapid hematopoietic recovery after peripheral-blood stem-cell transplantation.

PURPOSE: To study whether there is a relationship between transplanted cell dose and rate of hematopoietic recovery after peripheral-blood stem-cell (PBSC) transplantation, and to obtain an indication whether specific subsets of CD34+ cell populations contribute to rapid recovery of neutrophils or platelets. PATIENTS AND METHODS: Based on data from 59 patients, we calculated for each day after PBSC transplantation the dose of CD34+ cells that resulted in rapid recovery of either neutrophils or platelets in the majority (> 70%) of patients. Using dual-color flow cytometry, subsets of peripheral-blood CD34+ cells were quantified and the numbers of CD34+ cells belonging to each of the reinfused subsets correlated with hematopoietic recovery following high-dose chemotherapy. RESULTS: The calculated threshold values with a high probability of engraftment showed a steep dose-effect relationship between CD34+ cell dose and time to recovery of both neutrophils or platelets. Predominantly CD34+ cells with the phenotype of myeloid precursors were mobilized. A minority of CD34+ cells expressed the erythroid and megakaryocytic lineage-associated antigens and a low but distinct population of CD34+ cells expressed antigens associated with multipotent stem cells. Analysis showed that the number of CD34+CD33- cells (r = -.74, P < .05), as well as the number of CD34+CD41+ cells (r = -.81, P < .005), correlated significantly better with time to neutrophil and platelet recovery, respectively, than with the total number of CD34+ cells (r = -.55 and r = -.56, respectively). CONCLUSION: The numbers of CD34+CD33- cells and CD34+CD41+ cells may help to predict short-term repopulation capacity of PBSCs, especially when relatively low numbers of CD34+ cells per kilogram are reinfused.

Quantification of minimal residual disease in children with oligoclonal B-precursor acute lymphoblastic leukemia indicates that the clones that grow out during relapse already have the slowest rate of reduction during induction therapy.

Antigen receptor gene rearrangements are applied for the PCR-based minimal residual disease (MRD) detection in acute lymphoblastic leukemia (ALL). It is known that ongoing rearrangements result in subclone formation, and that the relapsing subclone(s) can contain antigen receptor rearrangement(s) that differ from the rearrangements found in the major clone(s) at diagnosis. However, the mechanism leading to this so-called clonal evolution is not known, particularly at which time point in the disease the relapsing subclone obtains its (relative) therapy resistance. To obtain insight in clonal evolution, we followed the kinetics of several subclones in three oligoclonal ALL patients during induction therapy. Clone-specific nested PCR for immunoglobulin heavy chain or T cell receptor delta gene rearrangements were performed in limiting dilution assays on bone marrow samples taken at diagnosis, at the end of induction therapy and at possible relapse in three children with oligoclonal B-precursor ALL. We demonstrated that in all three patients the subclones were behaving differently in response to therapy. Moreover, in the two patients who relapsed, the clones that grew out during relapse showed the slowest regression or even evoluated during induction therapy and the clones that were not present at relapse showed good response to induction therapy. These results support the hypothesis that at least in some patients already at diagnosis or in the very first weeks, subclones have important differences in respect to resistance. Hence, these data give experimental evidence for the need to develop, during the first months after diagnosis, quantitative PCR assays for at least two different Ig/TCR gene rearrangement targets for every ALL patient.

IgH/TCR delta PCR oligonucleotide liquid hybridization, a fast and sensitive assay for monitoring minimal residual disease in childhood B-precursor ALL.

The detection of minimal residual disease (MRD) in childhood B-precursor acute lymphoblastic leukemia (ALL) by polymerase chain reaction (PCR) may turn out to be a powerful tool in the evaluation and guidance of therapy. Most previously described techniques are highly sensitive but also too laborious for application in a routine setting. Here we describe a technique based on the determination of IgH VHDJH and TCR V delta 2D delta 3 junctional regions by PCR/cycle sequencing analysis and hybridization of junctional region oligonucleotide probes in a standard liquid hybridization (LH) assay. We systematically analyzed the applicability of this simplified approach for the monitoring of MRD in a large patient group. IgH VHDJH and TCR V delta 2D delta 3 junctional regions were amplified from presentation bone marrow samples obtained from 53 childhood B-precursor ALL patients. The combined approach allowed the identification of at least one tumor marker for 49/53 (92.5%) of patients. A total of 75 oligonucleotide probes (54 DJH, 21 V delta 2D delta 3) was tested in the LH assay. Sensitivity range was 10(-2)-10(-5) and 10(-4)-10(-5) for DJH and V delta 2D delta 3 junctional region probes, respectively. A sensitivity of at least one malignant cell in 10(4) normal cells was obtained for 84.8% of evaluable patients, applying on average 1.1 IgH and 0.47 TCR delta probes per patient. Comparison to a method based on the use of initial PCR product as clone-specific probe showed that oligonucleotide LH was one log more sensitive in six of nine patients tested. The presented technique allows the monitoring of MRD with acceptable sensitivities in over 90% of childhood B-precursor ALL patients. Moreover, the technique is suitable for prospective patient studies in a routine setting as it is fast, reproducible and makes use of a standard hybridization protocol for different oligonucleotide probes.

Clonal evolution of immunoglobulin heavy chain rearrangements in childhood B-precursor acute lymphoblastic leukemia after engraftment in SCID mice.

We grafted childhood B-precursor acute lymphoblastic leukemia (ALL) bone marrow (BM) cells into mice with severe combined immunodeficiency (SCID), in order to study the clonal evolution of immunoglobulin heavy chain (IgH) rearrangements in the absence of selective pressure by chemotherapy. BM cells from nine patients (six diagnosis samples and three relapse samples) were intravenously injected into SCID mice (three mice for each patient). All mice injected with cells from four patients developed a leukemia-like illness 12-40 weeks after injection. By PCR, new subclones that were the result of ongoing IgH rearrangement according to the mechanism operative in the injected cell populations (VH-replacement or VH to D-JH joining) were detected in the engrafted cell populations for all four patients. Subclones were mouse-specific, suggesting that subclone formation is a continuous process. Southern analysis after engraftment was unaltered as compared to the injected cells for one patient and revealed changes indicative of altered clonal composition for three patients. For two patients the observed changes possibly reflect the initial engraftment of a limited number of cells and occurred without changes in other parameters of the engrafted cell population, such as time needed for the development of leukemia, macroscopic organ involvement, immunophenotype and S-phase fraction. In one patient, we demonstrated the selective outgrowth of only a single cell type present at diagnosis, as characterized by IgH rearrangements. Our data show that evolution of clonal IgH rearrangements in B-precursor ALL may occur without the selective pressure of chemotherapy. Additionally, in some patients subclones present at diagnosis, as defined by IgH rearrangements, also possess different biological properties.

Rearrangement status of the malignant cell determines type of secondary IgH rearrangement (V-replacement or V to DJ joining) in childhood B precursor acute lymphoblastic leukemia.

Immunoglobulin heavy chain (IgH) oligoclonality in childhood B precursor acute lymphoblastic leukemia (ALL) as determined by Southern analysis is found in 30-50% of patients and has been shown to be the result of ongoing IgH rearrangement (mostly V(H)-replacement and V(H) to D-J(H) joining) after malignant transformation. It is unknown however, what determines the type of secondary rearrangement. Also the biological basis of the variable degree of oligoclonality observed in childhood ALL is poorly understood. We analyzed in detail the IgH rearrangement status of the leukemic cells for a random panel of 18 childhood B precursor ALL patients by polymerase chain reaction (PCR)/sequencing analysis and by Southern analysis. By Southern analysis 10/18 (55.6%) patients were considered oligoclonal and 8/18 (44.4%) monoclonal. In contrast, by PCR minor clonal rearrangements were detected in 14/18 (77.8%) patients. V(H)-replacement was found in 7/14 patients, V(H) to D-J(H) joining in 6/14 patients and an unusual type of secondary rearrangement, V(H)-D to J(H) joining, in one patient. Only a single type of secondary rearrangement was detected in each patient. The type of secondary rearrangement (V(H)-replacement or V(H) to D-J(H) joining) depended on the rearrangement status (VDJ/VDJ or VDJ/DJ, respectively) of the dominant leukemic clone as determined by Southern analysis. We found that in addition to a more 'advanced' IgH rearrangement status patients with V(H)-replacements also have a more 'advanced' TCRdelta rearrangement status, which possibly reflects exposure of both the IgH locus and the TCRdelta locus to recombinase activity in a preleukemic clone. Finally, we investigated a putative relationship between oligoclonality by Southern analysis and S-phase fraction of the leukemic cell population. We found a significantly lower percentage cells in S-phase for oligoclonal patients as compared to monoclonal patients. Our data add to the understanding of ongoing rearrangement of antigen receptor loci in childhood ALL and have implications for the monitoring of minimal residual disease by PCR.

Prolonged persistence of PCR-detectable minimal residual disease after diagnosis or first relapse predicts poor outcome in childhood B-precursor acute lymphoblastic leukemia.

The follow up of minimal residual disease (MRD) in childhood B-precursor ALL by polymerase chain reaction (PCR) may be of help for further stratification of treatment protocols, to improve outcome. However, the clinical relevance of this approach has yet to be defined. We report the retrospective follow-up of MRD in bone marrow (BM) samples from 50 childhood B-precursor ALL patients by IgH/TCR delta PCR. Twenty-two patients remained in continuous complete remission (median follow-up 61 months), and 28 experienced relapse (median follow-up 75 months). Initial regression of MRD on therapy correlated with outcome. At the end of induction therapy 2/18 (11.1%) patients from the CCR group were PCR positive vs 10/16 (62.5%) from the 'relapse' group (P = 0.005). The presence of PCR detectable MRD predicted event-free survival independent of standard clinical and cytogenetical parameters. Also subsequent to first BM relapse, a correlation between MRD regression and outcome was observed. Six of eight patients who became PCR negative in the time period between relapse and bone marrow transplantation are in CCR, whereas 7/7 patients who remained PCR positive in this time period died (P = 0.006). In approximately 70% of evaluable patients, clinical relapse was preceded by recurrence of detectable MRD at time intervals of 3-18 months earlier and the recurrence of PCR positivity after a period of negativity was always followed by overt relapse. At relapse, the combined use of IgH and TCR delta probes reduced false negativity caused by clonal evolution to approximately 10%. This study shows that the evolution of PCR detectable MRD is an independent predictor of outcome.

The nature of toxicity of human serum in the bioassay for erythropoietin using mouse foetal liver cells.

Using several immunological techniques, it was possible to demonstrate that toxicity of human serum in the foetal mouse liver cell bioassay for erythropoietin was due to complement-dependent IgM hetero antibodies to mouse foetal liver cells. The titre of the antibodies in 50 normal human sera ranged between 2 and 64 as measured in an agglutination test with mouse erythrocytes. Specificity of the antibodies for the ABO-or Ii-blood group system could not be established. Inactivation of complement by heating a serum for 30 minutes at 56 degrees C abolished toxicity.

Increased migration of cord blood-derived CD34+ cells, as compared to bone marrow and mobilized peripheral blood CD34+ cells across uncoated or fibronectin-coated filters.

Hematopoietic progenitor cells (CD34+ cells) migrate to the bone marrow after reinfusion into peripheral veins. Stromal cell-derived factor-1 (SDF-1) is a chemokine produced by bone marrow stromal cells that induces migration of CD34+ cells. In this study we compared spontaneous and SDF-1-induced migration of CD34+ cells from bone marrow (BM), peripheral blood (PB), and cord blood (CB) across Transwell filters. Under all circumstances, CB CD34+ cells showed significantly more migration than did BM or PB CD34+ cells. SDF-1 induced migration of BM CD34+ cells was higher than that of PB CD34+ cells, possibly due to differences in sensitivity towards SDF-1. Indeed, PB CD34+ cells showed a significantly lower expression of the receptor for SDF-1 (CXCR-4) than did BM and CB CD34+ cells. The sensitivity to SDF-1, as measured by migration towards different concentrations of SDF-1, was identical for BM and CB-derived CD34+ cells and correlated with their equal CXCR-4 receptor expression. Coating of the filters with the extracellular matrix protein fibronectin (FN) strongly enhanced the SDF-1-induced migration of PB CD34+ cells (2.5 times) and of BM CD34+ cells (1.5 times). SDF-1 induced migration of PB CD34+ cells over FN-coated filters was blocked by antibodies against beta1 integrins. Subsequently, analysis was performed to determine whether SDF-1 preferentially promoted migration of subsets of CD34+ cells. Actively cycling CD34+ cells, which were present in BM (14%) but hardly in PB (2.2%) or CB (1.2%), were found to migrate preferentially towards SDF-1. In the input, 14%+/-2.5% of the BM CD34+ cells were in G2/M and S phase, whereas in the migrated fraction 20%+/-5.7% of the cells were actively cycling (p < 0.05). We did not observe preferential migration of phenotypically recognizable primitive CD34+ subsets, despite the fact that CB CD34+ cells are thought to contain a higher percentage of immature subsets. In conclusion, the relatively lower migration of PB CD34+ cells seems to be due to a lower sensitivity towards SDF-1, and the higher migrational capacity of CB CD34+ cells, in comparison to BM and PB CD34+ cells, seems to have an as yet unknown intrinsic cause. The increased migration of CB CD34+ cells may favor homing of these cells to the bone marrow, which might reduce the number of cells required for hematological reconstitution after transplantation.

Differences in megakaryocyte expansion potential between CD34(+) stem cells derived from cord blood, peripheral blood, and bone marrow from adults and children.

OBJECTIVE: Reinfusion of ex vivo expanded autologous megakaryocytes together with stem cell transplantation may be useful to prevent or reduce the period of chemotherapy-induced thrombocytopenia. We compared the megakaryocyte expansion potential of CD34(+) stem cells derived from different sources: cord blood (CB), peripheral blood (PB), bone marrow from adults (ABM), and bone marrow from children (ChBM). Three different growth factor combinations were tested to identify the best combination for each of the sources. MATERIALS AND METHODS: CD34(+) cells were isolated from CB, PB, ABM, or ChBM and cultured in an in vitro liquid culture system in the presence of thrombopoietin (Tpo), Tpo + interleukin (IL-1), or Tpo + IL-3. After 8 days, proliferation was determined and the cultured cells were identified with lineage-specific surface markers by flow cytometry. RESULTS: Cultures with ChBM-derived CD34(+) cells showed the lowest level of expansion of megakaryocytes and gave rise to more profound formation of myeloid and monocytic cells. In cultures with BM- or PB-derived cells, presence of IL-3 reduced the number of immature megakaryocytes (CD34(+)CD41(+) cells). However, in CB cultures, the number of CD34(+)CD41(+) cells was highest in cultures with Tpo + IL-3. Overall, cultures with CB CD34(+) cells yielded the highest number of megakaryocytes, but these cells showed reduced ploidization and lower level of CD41 expression, suggesting less maturation. CONCLUSIONS: Each of the different CD34(+) cell sources responded differently to cytokine stimulation. For PB and ABM, the cytokine combination Tpo + IL-1 is most suitable to obtain high numbers of both immature and mature megakaryocytes for transfusion purposes. For CB, Tpo + IL-3 is better.

Interleukin-6 is a survival factor for committed myeloid progenitor cells.

In this study, we investigated the effect of recombinant human interleukin-6 (IL-6) on colony-forming cells for granulocytes and macrophages (CFU-GM) cultured in suspension. IL-6 when used alone did not induce proliferation of highly purified CD34+ human hematopoietic progenitors. Moreover, no influence of IL-6 was observed on the proliferation induced by granulocyte-macrophage colony-stimulating factor (GM-CSF) or granulocyte (G)-CSF. However, a marked survival enhancement (GM-CSF 228 +/- 42%, p < 0.01, and G-CSF 137 +/- 9%, p < 0.05) was observed when CD34+ cells were preincubated with IL-6 for 6 days. This survival effect became even more pronounced under serum-poor conditions (GM-CSF 380 +/- 80%, p < 0.01, and G-CSF 180 +/- 20%, p < 0.01) and could also be demonstrated at the single cell level in a colony-forming assay. By analysis of subpopulations of CD34+ bone marrow (BM) cells selected on the basis of CD45RO expression, the observed IL-6-mediated survival effect was found to be restricted to the CFU-GM containing CD45RO- subset. Our data show that IL-6 is a survival factor for CFU-GM.

Effective purging of bone marrow by a combination of immunorosette depletion and complement lysis.

The effectiveness of a simple immunorosette technique for the depletion of common acute lymphatic leukemic (cALL) blasts from autologous bone marrow transplants was studied. Erythrocytes were sensitized with tetramolecular complexes consisting of rat anti-mouse IgG1 monoclonal antibodies (McAbs) that crosslink two different mouse McAbs. One of the McAbs was directed against glycophorin A, and the other was directed against marker glycoproteins of B cells and their precursors (CD9, CD10, CD19, or CD22). Immunorosettes were formed by addition of the sensitized erythrocytes to the cALL+ cells. After density-gradient separation of immunorosettes from mixtures of cALL+/terminal deoxynucleotidyl transferase-positive (TdT+) leukemic blasts and mononuclear bone marrow cells, nearly a 2-log depletion of leukemic cells was measured by flow cytometry. Clonogenic assays with two cALL+B-cell lines (Ros-17 and Nalm-16) were performed to compare the efficacy of complement-mediated cell lysis, immunorosette depletion, and a combination of both procedures. Complement-mediated cytotoxicity with the three McAbs in combination with baby rabbit complement yielded a 1- to 2-log cell kill. Immunorosette depletion resulted in a 3-log reduction of clonogenic units. Sequential application of the two methods (immunorosette depletion with CD19 McAb followed by a complement lysis with CD9 and CD10 McAbs) led to superior results in causing a 4- to 5-log purging effect. These purging procedures did not cause a loss of normal myeloid (granulocyte-macrophage colony-forming units, CFU-GM) or erythroid (erythroid burst-forming units, BFU-e) progenitors from the bone marrow. This study indicates that the combination of the two methods results in a highly efficient purging procedure for the removal of cALL+ cells from autologous bone marrow cells.

Combined measurement of growth and differentiation in suspension cultures of purified human CD34-positive cells enables a detailed analysis of myelopoiesis.

In this study we have made a detailed analysis of growth factor (granulocyte-macrophage colony-stimulating factor [GM-CSF], granulocyte colony-stimulating factor [G-CSF], and macrophage colony-stimulating factor [M-CSF])-induced proliferation and differentiation of highly purified CD34+ committed human myeloid progenitor cells in suspension cultures. The results were compared with colony formation in semisolid medium. Proliferation in suspension cultures was determined by means of incorporation of [3H]thymidine, differentiation by flow cytometric immunophenotyping using a panel of monoclonal antibodies against monomyeloid antigens, and by morphology. A good correlation was found between the number of granulocyte-macrophage colony-forming units (CFU-GM) in semisolid medium and [3H]thymidine incorporation in suspension (r = 0.82), both assessed at day 11. Moreover, the frequency of proliferating cells as determined in suspension cultures by limiting dilution analysis was similar to the frequencies of CFU-GM as measured in semisolid medium. Studies on GM-CSF- and G-CSF-induced cell-growth kinetics revealed distinct proliferation patterns. Immunophenotypically the subsequent induction of the mature granulocytic antigens CD15 and CD67 was observed to be accompanied by a gradual loss of the HLA-DR antigen, whereas little monocytic differentiation was observed. M-CSF, although inducing no colony formation of CD34+ cells and minimal proliferation in suspension, induced monocytic differentiation, demonstrated by the expression of HLA-DR, CD14, and CD36 in the absence of CD15 and CD67. The observed immunophenotypical profiles were confirmed by the results of cytological characterization. Thus, the combined measurement of growth factor-induced proliferation and differentiation of progenitor cells in suspension cultures can be a useful alternative for the CFU-GM assay. Moreover, because small numbers of cells are required, it allows for detailed studies on cell-growth kinetics and developmental stages within the granulocytic and monocytic lineages.

Adhesion of hematopoietic progenitor cells to human bone marrow or umbilical vein derived endothelial cell lines: a comparison.

Homing of hematopoietic progenitor cells (HPC) to the bone marrow may be mediated by adhesion molecules specifically expressed on human bone marrow endothelial cells (HBMEC). This hypothesis suggests that HPC would preferentially bind to HBMEC compared to endothelial cells from other origins. In this study, HPC were allowed to adhere either to HBMEC cell lines or to human umbilical vein endothelial cells (HUVEC) in two different experimental set-ups. First, adherence was measured using a flow cytometric assay with three different colors identifying each cell population (HPC, HBMEC, HUVEC). HPC could adhere (in a competitive way) to the two endothelial cell lines under stirring conditions, which simulated adhesion under shear stress, as present in blood vessels. Because this assay requires relatively firm adhesion and the endothelial cells don't form a monolayer, we studied the same interactions under less stringent conditions. HPC were allowed to adhere to endothelial monolayers under gently rocking conditions. Differential adhesion of HPC to a set of endothelial cell lines did not correlate with the origin of the endothelial cells. Adhesion of HPC to both types of endothelial cells was inhibited in the presence of various combinations of monoclonal antibodies against the adhesion molecules VLA-4, CD18, and/or E-selectin. No indications were obtained for qualitative differences in the role of these molecules in adhesion of HPC to either HBMEC or HUVEC cell lines. In conclusion, no preferential adhesion of HPC to HBMEC compared to HUVEC cells was observed. This may be due to a lack of origin-specific differences between endothelial cells, implying that the specificity of homing is not regulated at the entrance of the bone marrow. Otherwise, the origin-specific differences between endothelial cells of different origins may be microenvironment-induced, rather then intrinsic, implying that care should be exercised with the use of endothelial cell lines in studies investigating the specificity of homing of HPC.

Substrate and inhibitor studies on proteinase 3.

Various amino acid and peptide thioesters were tested as substrates for human proteinase 3 and the best substrate is Boc-Ala-Ala-Nva-SBzl with a kcat/Km value of 1.0 x 10(6) M-1.s-1. Boc-Ala-Ala-AA-SBzl (AA = Val, Ala, or Met) are also good substrates with kcat/Km values of (1-4) x 10(5) M-1.s-1. Substituted isocoumarins are potent inhibitors of proteinase 3 and the best inhibitors are 7-amino-4-chloro-3-(2-bromoethoxy)isocoumarin and 3,4-dichloroisocoumarin (DCI) with kobs/[I] values of 4700 and 2600 M-1.s-1, respectively. Substituted isocoumarins, peptide phosphonates and chloromethyl ketones inhibited proteinase 3 less potently than human neutrophil elastase (HNE) by 1-2 orders of magnitude.

Determination of proteinase 3-alpha 1-antitrypsin complexes in inflammatory fluids.

Physiological inhibitors were tested for their in vitro interaction with neutrophil proteinase 3 (PR3). The major plasma proteinase inhibitor of PR3 is alpha 1AT. We have developed a radioimmunoassay (RIA) for quantitative detection of PR3-alpha 1AT complexes formed in vivo in inflammatory exudates such as synovial fluid and plasma from patients with sepsis. Levels of PR3-alpha 1AT complexes correlated significantly with levels of human neutrophil elastase (HNE)-alpha 1AT complexes. Thus, in vivo alpha 1AT not only protects against excessive HNE activity, but also against excessive PR3 activity.

Evaluation of a method of production and purification of monoclonal antibodies for clinical applications.

A procedure is described for the purification of monoclonal antibodies (Mab) from ascitic fluids, which meets the quality control required for in vivo applications of immunoglobulins (Ig) in man. Additional assays were performed to calculate viral and DNA content of the purified Mab. These studies are important to prevent the possible side effects, oncogenic events and virus-related diseases which could follow immunotherapy with Mab.

A monoclonal antibody to the human platelet glycoprotein IIb/IIIa complex induces platelet activation.

The platelet glycoprotein (GP) IIb/IIIa complex functions as the receptor for fibrinogen on activated platelets. The effects of two anti-GPIIb/IIIa monoclonal antibodies on platelet function were studied. These antibodies, 6C9 and C17, recognized different epitopes, which were exclusively present on the undissociated GPIIb/IIIa complex. Whereas C17 inhibited the binding of fibrinogen to platelets and platelet aggregation induced by adenosine diphosphate (ADP) or collagen, 6C9 caused irreversible aggregation of platelets, both in the presence and absence of extracellular fibrinogen. When incubated with unstirred (non-aggregating) platelets, 6C9 induced release of alpha and dense granule-constituents as well as binding of 125I-fibrinogen to platelets. The latter was evidently mediated in part by platelet-derived ADP, since it was inhibited to a large extent by apyrase, the ADP-hydrolyzing enzyme. F(ab')2 fragments of 6C9 did not induce platelet-release reactions but caused (slow) aggregation of platelets in the presence of extracellular fibrinogen. These results indicate that binding of an antibody to a specific site on the platelet GPIIb/IIIa complex may cause fibrinogen-mediated aggregation. The Fc part of the platelet-bound antibody appears to be involved in the induction of platelet release.