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B Axelsson

Publications and source records attributed to B Axelsson.

At least 19 recordsLinked to original sources
PubMed1992

Agonistic properties of anti-B cell antibodies purified on staphylococcal protein A may be due to contaminating protein A.

Some antibodies directed to cell surface receptors may mimic the physiological ligands by inducing the transmission of activation or growth signals. Such agonistic antibodies have proven very useful when studying functional properties of various receptor molecules on, e.g., lymphoid cells. However, while investigating the agonistic effects on tonsillar B cells of the anti-CD43 monoclonal antibody (mAb) D4B11 and the anti-CD40 mAb S2C6, we made some observations which emphasize the need for caution when using antibodies purified by protein A affinity chromatography. Both antibody preparations were found to elicit changes in the intracellular free calcium concentration ([Ca2+]i) as well as promoting proliferation of phorbol ester activated cells. However, a closer analysis showed that the increase in [Ca2+]i could be attributed to soluble staphylococcal protein A (SpA) desorbed during antibody purification. By using pure soluble SpA, we were able to show that nanogram amounts were sufficient to increase [Ca2+]i by a mechanism that involved both a mobilization from intracellular stores and an influx across the B cell membrane. A similar effect on cytosolic Ca2+ in B cells was also noted for streptococcal protein G (protein G), another bacterial component used for antibody purification. However, in contrast to SpA, protein G had little effect on cell proliferation. These observations suggest that the presence of trace amounts of SpA or protein G in antibodies purified on these bacterial components may lead to incorrect interpretations of the agonistic properties of such antibodies. When the above findings were taken into account, it was found that the CD43 mAb D4B11, like the CD40 mAb S2C6, stimulated growth of B cells without causing any measurable increase in [Ca2+]i. Both CD40 and CD43 may thus be coupled to signalling pathways which do not involve breakdown of membrane phosphoinositides.

Antibodies, Monoclonal↗
PubMed1992

Interleukin-4-mediated aggregation of anti-IgM-stimulated human B cells: inhibition of aggregation but enhancement of proliferation by antibodies to LFA-1.

Direct cellular interactions, involving adhesion structures like lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1), play a critical role in the initial stages of T-cell-dependent B-cell activation. However, the relevance of cellular contact in later, lymphokine driven stages of B-cell stimulation is less well understood. We have here studied the ability of different lymphokines [interleukin (IL)-1 alpha, IL-1 beta, IL-2, IL-3, IL-4, IL-6 and interferon-gamma (IFN-gamma)] to stimulate adhesion processes as well as proliferation of highly purified tonsillar B lymphocytes. None of the lymphokines were by themselves able to induce aggregation in resting B cells but, when added together with anti-IgM, IL-4 and to a lesser extent IL-2, promoted the formation of large, dense aggregates which were macroscopically visible after 3-4 days in culture. Addition of anti-LFA-1 antibodies (anti-CD11a or CD18) completely inhibited the lymphokine-promoted aggregation, indicating that cluster formation was mediated by LFA-1. Fluorescence-activated cell sorter (FACS) analysis showed that the expression of both LFA-1 and ICAM-1 increased after stimulation with IL-4 as well as with IFN-gamma. However, in contrast to IL-4, IFN-gamma did not enhance cellular aggregation, suggesting that qualitative rather than quantitative changes in LFA-1/ICAM-1 promote aggregation. Although anti-LFA-1 antibodies inhibited aggregation of both IL-2- and IL-4-stimulated cells they did not inhibit proliferation. In contrast, in IL-4-stimulated cultures inhibition of cell contact resulted in a significantly increased proliferation. Furthermore, IFN-gamma-stimulated cells responded with proliferation in the absence of aggregation. Taken together, the findings suggest that LFA-1-dependent cellular contact plays a minor role in lymphokine driven B-cell proliferation. The possible importance of aggregation in B-cell differentiation is discussed.

Antibodies, Anti-Idiotypic↗
PubMed1991

Calculation of affinity constants directly from homologous displacement curves.

Homologous displacement experiments are described in which the binding of labelled ligand (tracer) was inhibited with the same ligand unlabelled (inhibitor). Data were evaluated with a direct curve-fitting method. The equation used employs the concentration of unlabelled ligand as the independent variable and the fraction of tracer bound (p) as the dependent variable. The other entities of the equation are the dissociation constant (Kd), the maximal fraction of tracer bound (Po) and the tracer concentration (T). Different options exist regarding the insertion of Po and T as parameters or constants in the curve-fitting. When applied to experimental data obtained from the binding of dinitrophenyl-hapten by a monoclonal antibody, the least interexperimental variation in affinity was obtained when both Kd and Po were estimated as parameters, and T was inserted as a constant. This calculation procedure achieves more reproducible results than those obtained with the Scatchard plot and the Langmuir curve, even after exclusion of the most scattered data points.

Antibodies, Monoclonal↗
PubMed1991

Expression of CD40 and CD43 during activation of human B lymphocytes.

CD40 and CD43 are two cell-surface glycoproteins that appear to be functionally involved in the growth stimulation of human B cells. Whereas CD40 is structurally similar to the NGF receptor and is present on all resting B cells, CD43 displays no homology to other known proteins and is expressed only on a subpopulation of these cells. To further understand the extra- and intracellular signals regulating these molecules and in which stage of activation they may play a role, we used various activation strategies and studied their expression on tonsillar B cells. As expected, activation of protein kinase C by TPA increased both CD40 and CD43. In contrast, a rise in intracellular Ca2+, e.g. by ionomycin, did not influence the expression of these antigens. However, in the presence of TPA, ionomycin further up-regulated CD43 but not CD40. Anti-IgM behaved similarly to ionomycin suggesting that the effect of this reagent was due primarily to its ability to increase intracellular Ca2+. Of three interleukins (IL-2, IL-4 and IL-6) only IL-4 had a significant effect when used alone in that it up-regulated CD40 but not CD43. However, in the presence of anti-IgM, both IL-2 and IL-4 synergistically up-regulated the two antigens. Complementation of antigen receptor stimulation with TPA or IL-4 increased CD40 during the first 24 h, whereas up-regulation of CD43 did not occur until 24 to 48 h after stimulation. With regard both to up-regulation in response to different stimuli and to kinetics, CD40 expression paralleled that of the early activation antigen CD23, whereas CD43 was induced in parallel with the transferrin receptor (CD71). Taken together, our results suggests that the expression of CD40 and CD43 is regulated by different intracellular signals and that CD40 may be important during early activation, whereas CD43 may have its major function during later stages of B-cell differentiation. These assumptions are in line with the observations that CD40 antibodies can directly activate resting B cells and that CD43 are retained on plasma cells.

Antibodies↗
PubMed1991

Quantitative evaluation of four 99Tcm colloids for bone marrow scintigraphy using single photon emission computed tomography.

Colloids used for bone marrow scintigraphy are also taken up in the liver and spleen. The liver activity in particular hampers interpretation of the study. In this study, four small-sized commercial colloids labelled with 99Tcm were compared for bone marrow uptake relative to the liver, spleen and background activity. Three human albumin colloids (Microlite, E.I. du Pont de Nemours & Co; Solco Nanocoll, Solco Nuclear; TCK-9, International CIS) and one antimony sulphide colloid (TechneScan Sb2S3, Mallinckrodt Diagnostics) were compared. The study was performed in patients routinely referred for liver/spleen scintigraphy who had a normal result. Each examination was carried out using single photon emission computed tomography. After correction for attenuation and scattering of photons, the activity of the bone marrow of the lumbar spine was related to the liver, spleen and background activity. The bone marrow/liver activity quotient of Solco Nanocoll and TCK-9 was almost twice the value for Microlite and TechneScan Sb2S3. The bone marrow/spleen quotient was almost four times higher and the bone marrow/background quotient almost twice as high for Solco Nanocoll as for the other three colloids, between which there were no significant differences.

Antimony↗
PubMed1991

Multiple-beam equalization radiography in chest radiology. Image quality and radiation dose considerations.

The large difference in transmission between the mediastinum and the part of the chest mainly containing lungs causes major problems in chest radiography. A system for advanced multiple beam equalization radiography has been evaluated. Evaluation of image quality has been performed both using standard phantoms and from clinical radiographs. Measurements of radiation dose burden to the patient have been made both in clinical examinations and using an anthropomorphic phantom. The image quality, in areas with low transmission, is substantially increased using the equalization system. In parts of the chest mainly containing lung tissue, conventional systems show an equal or slightly better image quality. The radiation dose burden to the patient is increased by 25 percent using the equalization system, as compared to a low-dose air-gap system. In our opinion, the slight increase in radiation dose burden is well motivated by the high overall quality of the radiographs produced.

Humans↗
PubMed1990

Comparison of In-111 granulocytes and Tc-99m albumin colloid for bone marrow scintigraphy by the use of quantitative SPECT imaging.

A comparison of In-111 oxinate labeled autologous granulocytes and Tc-99m albumin colloid for bone marrow scintigraphy is reported. The aim of this report was to determine if the intense uptake in the liver and spleen with nano-sized colloids, which hampers the evaluation of the skeletal parts surrounding the liver, is reduced by the use of radiolabeled granulocytes. This study is based on a retrospective analysis of 19 abdominal tomographic examinations with In-111 granulocytes performed to detect septic foci. After correction for attenuation and scattering of photons was performed, the uptake in the bone marrow of the lumbar spine was seen to be related to the liver, spleen, and tissue background activity. The results in this study were compared with corresponding data from 20 normal liver/spleen tomographic examinations performed with Tc-99m nanocolloid, which is routinely used for bone marrow scintigraphy. The bone marrow/liver activity ratio for granulocytes varied, but it exceeded the corresponding mean ratio for colloid in all examinations. The mean values for granulocyte uptake 3 and 20 hours after injection was, respectively, about 6 and almost 10 times higher than were those for colloid. The activity ratios between bone marrow and spleen as well as between bone marrow and tissue background was not improved and or may even have been reduced by the use of granulocytes. It is suggested that granulocytes labeled in vitro by Tc-99m hexamethylpropylene amineoxime (HMPAO) or in vivo by monoclonal antigranulocyte antibodies may provide techniques for improved bone marrow imaging.

Adult↗
PubMed1990

Intrapulmonary deposition of aerosolized Evans blue dye and liposomes in an experimental porcine model of early ARDS.

In early ARDS (Adult Respiratory Distress Syndrome) and other inflammatory pulmonary disorders the lung might benefit from a high local deposition of an active drug, in order to optimize the local concentration without systemic side effects. In this methodological study we used pigs under controlled ventilation. The study was carried out in two steps. In the first part Evans blue dye in NaCl was delivered in aerosolized form. In the second part a dry powder containing FITC (fluorescein-isothiocyanate)-labelled-liposomes in NaCl was delivered in the same way. We evaluated whether there was an even, central, peripheral and/or alveolar deposition, whether the procedure was reproducible, and whether there was an interaction with alveolar macrophages. Sixteen animals under chlormethiazole anaesthesia and intermittent positive pressure ventilation (IPPV) were included in the study. Four animals were sacrificed after nebulization and baseline measurements. Five animals served as controls and received saline i.v. Six animals received endotoxin i.v. (18 micrograms.kg-1.h-1). One animal underwent broncho-alveolar lavage 15 min and 2 h after liposome administration. At the end of each experiment the lungs were inflated with air, excised and dried in a microwave oven. The left lung of each animal was sliced in a reproducible manner and lung-pieces from different regions were analyzed. The Evans blue dye or the phospholipid fraction of the lungs (containing liposomes), was extracted and analyzed spectrofluorometrically. This study shows that it is possible, under reproducible conditions, to administer aerosolized Evans blue dye and liposomes and to achieve a deposition in the terminal airways and/or alveolar spaces. The broncho-alveolar lavage demonstrated an interaction of liposomes with alveolar macrophages. The results imply that liposomes carrying active drugs and administered by inhalation may be used for local pulmonary treatment in early ARDS and other related inflammatory pulmonary diseases.

Aerosols↗
PubMed1990

Niobium filters for dose reduction in pediatric radiology.

The performance of a niobium filter, with K-edge at 19 keV, and a copper filter have been studied concerning absorbed dose, image quality and tube loading. Absorbed doses were measured with TLD. To evaluate image quality a perspex phantom with image quality test objects was used. In comparison with a conventional filter made of copper no significant advantage was obtained with the niobium filter.

Copper↗
PubMed1989

Some physical factors influencing the accuracy of convolution scatter correction in SPECT.

Some important physical factors influencing the accuracy of convolution scatter correction techniques in SPECT are presented. In these techniques scatter correction in the projection relies on filter functions, QF, evaluated by Fourier transforms, from measured scatter functions, Qp, obtained from point spread functions. The spatial resolution has a marginal effect on Qp. Thus a single QF can be used in the scatter correction of SPECT measurements acquired with the low energy high resolution or the low energy general purpose collimators and over a wide range of patient-collimator distances. However, it is necessary to examine the details of the shape of point spread functions during evaluation of Qp. QF is completely described by scatter amplitude AF, slope BF and filter sum SF. SF is obtained by summation of the values of QF occupying a 31 x 31 pixels matrix. Regardless of differences in amplitude and slope, two filter functions are shown to be equivalent in terms of scatter correction ability, whenever their sums are equal. On the basis of filter sum, the observed small influence of ellipticity on QF implies that an average function can be used in scatter correcting SPECT measurements conducted with elliptic objects. SF is shown to increase with a decrease in photon energy and with an increase in window size. Thus, scatter correction by convolution may be severely hampered by photon statistics when SPECT imaging is done with low-energy photons. It is pointless to use unnecessarily large discriminator windows, in the hope of improving photon statistics, since most of the extra events acquired will eventually be subtracted during scatter correction. Regardless of the observed moderate reduction in SF when a lung-equivalent material replaces a portion of a water phantom, further studies are needed to develop a technique that is capable of handling attenuation and scatter corrections simultaneously. Whenever superficial and inner radioactive distributions coexist the observed reduction of SF close to the phantom surface indicates that scatter correction of such distributions has to rely on two distinct filter functions. Corrections based on a surface function produce accurate results in the superficial region, while the central distributions are substantially overestimated. Surface radioactive distributions introduce appreciable errors in the determination of central distributions when corrections are based on central filter function. This function introduces a reduction of about 40% in the measured surface concentration.

Humans↗
PubMed1989

Studies on the role of CD43 in human B-cell activation and differentiation.

The monoclonal antibody (MoAb) B1B6 to human leucocyte sialoglycoprotein, CD43, induces aggregation of T cells and delivers progression signals early during activation of both T and B cells in the presence of primary activators of protein kinase C. In this report we further studied the role of CD43 in human B-cell activation and differentiation. About 5-10% of resting tonsillar B cells are CD43+. In the presence of TPA or antibodies to CDw40, the proportions of CD43+ cells drastically increased. The expression was optimal on day 3 of culture, when up to 80% and 50%, respectively, were CD43+. Whereas MoAb B1B6 together with TPA induced a three- to fivefold higher proliferative response as compared to TPA alone, antibodies to CDw40 did not synergize with MoAb B1B6 in B-cell proliferation. Tonsillar populations depleted of CD43+ B cells responded with lower proliferation to TPA alone or to TPA and B1B6 or anti-CDw40 antibodies. MoAb B1B6 did not affect the production of IgM or IgG as induced by pokeweed mitogen in the presence of autologous T cells, from either peripheral blood or tonsillar B cells. Neither did it affect the IgG production from the CD43+ BSF-2 sensitive Epstein-Barr virus-transformed lymphoblastoid cell line CESS. The results show that CD43 is upregulated on B cells during activation. Furthermore, CD43+ B cells are included in the population which responds to signals delivered by TPA, anti-CD43 or anti-CDw40 antibodies, and the proliferation of this population is not merely due to an expansion of the small population of CD43+ cells present among these cells. Moreover, the epitopes recognized by MoAb B1B6 are not involved in the differentiation of and ultimate Ig-secretion from activated B cells.

Antibodies, Monoclonal↗
PubMed1989

Enhancement of human B-cell proliferation by a monoclonal antibody to CD43.

Monoclonal antibodies (MoAb) to human leucocyte sialoglycoprotein, CD43, have been shown to deliver mitogenic signals to human T cells or to enhance T-cell proliferation induced by concanavalin A, anti-CD3 antibodies or phorbol ester. In this paper, we studied the effects of anti-CD43 MoAb B1B6 on the activation of human B cells. Anti-CD43 MoAb B1B6 was not mitogenic by itself for human B cells. However, when added together with TPA, both resting and in vivo activated tonsillar B cells, containing 5-10% and about 35% CD43+ respectively, responded with three- to fivefold higher proliferation compared to that obtained with TPA alone. A peak in the proliferative response was reached on day 3. Optimal proliferation was obtained when the antibody was present from the start of culturing. Addition of MoAb B1B6 together with a calcium ionophore, ionomycin, did not induce B-cell proliferation. Neither did mAb B1B6 sustain the growth of B cells that were already in the cell cycle, i.e. precultured with phorbol ester (PDB) and ionomycin for 3 days. The results are similar to those obtained with antibodies to CD22 and CD23 and show that early progression signals are delivered to resting B cells through CD43 in the presence of primary activators of protein kinase C.

Adjuvants, Immunologic↗
PubMed1989

Persistent superphosphorylation of leukosialin (CD43) in activated T cells and in tumour cell lines.

CD43 (leukosialin) is a highly sialylated, single-chain molecule expressed on most human leucocytes. Regulatory signals appear to be transduced through the molecule as suggested by the ability of anti-CD43 antibodies to induce aggregation and proliferation of T cells and to enhance B-cell proliferation and natural killer cell activity. Activation of protein kinases is an essential event in signal transduction. We were therefore interested to study whether CD43 may function as a substrate for protein kinases during mitogenic activation of lymphocytes. We show that CD43 was rapidly superphosphorylated (within minutes) on serine residues following addition of phorbol ester (PMA) to peripheral blood lymphocytes. PMA treatment of the cells was not followed by rapid down-regulation of CD43. Activation of the lymphocytes by concanavalin A or anti-CD3 antibodies (OKT-3) also resulted in superphosphorylation of CD43. However, the phosphorylation was delayed as compared to that induced by PMA and was detected 3-4 h after the addition of the reagents. A plateau was reached after 24-48 h of stimulation. Interestingly, the high level of phosphorylation of CD43 was maintained in long-term cultures of T cells activated by various means. Furthermore, CD43 was found to be constitutively superphosphorylated (on serine and tyrosine) in continuously growing cell lines of T, B, and non-lymphoid origin. Taken together, the results suggest that CD43 has an important role during both early and late phases of T-cell activation and that modulation of its biochemical properties by protein kinases may be associated with progression through the cell cycle and with cellular growth.

Antigens, CD↗
PubMed1988

Induction of aggregation and enhancement of proliferation and IL-2 secretion in human T cells by antibodies to CD43.

CD43 (large sialoglycoprotein) is a heavily glycosylated protein expressed on virtually all thymus-derived lymphocytes, on a subpopulation of B cells and on granulocytes. Recently, an anti-CD43 mAb (L10) was shown to induce proliferation in T cells comparable to that induced by anti-CD3. The L10 antibody was reported to react with both sialylated and desialylated CD43. In order to further elucidate the role of CD43 in various T cell functions we have studied the biologic properties of two other mAb (B1B6 and E11B, IgG1) directed against sialic acid-dependent epitopes on CD43. Addition of low amounts of antibody (5 to 10 ng/ml) to freshly isolated T cells or to T cell lines resulted in a rapid clustering of the cells. Fab fragments were also active albeit at a 10-fold higher concentration. Aggregation was dependent on active cell metabolism (inhibited by azide and at low temperatures), on the presence of divalent cations (Mg2+) and was inhibited by antibodies to CD18 but not by antibodies to CD11a (leukocyte function-associated Ag-1 alpha). B1B6 and E11B were poorly mitogenic when added alone in soluble form to PBL or to T cells. However, supernatants from cultures of PBL treated with B1B6 for 2 days contained IL-2 activity. No increase in the number of CD25+ cells was seen during the same period. Exogenously added IL-2 did not synergize with B1B6 or E11B in activation of PBL, whereas proliferation was significantly increased by the addition of the antibodies to activation systems with low endogenous production of IL-2 (PMA or soluble anti-CD3). The anti-CD43 antibodies amplified T cell proliferative responses induced by Con A or leukoagglutinin from Phaseolus vulgaris. F(ab')2 fragments enhanced proliferation significantly better than Fab fragments suggesting that cross-linking of CD43 molecules was an essential features of the amplifying signal. Compared with cultures activated by Con A alone, an increased number of CD25+ cells and of blast cells as well as an increased IL-2 production was observed in cultures activated by B1B6-Con A. The results indicate that regulatory signals, which may function to modify homo- or heterotypic T cell adhesion as well as autocrine production of IL-2, can be transduced through CD43.

Antibodies, Monoclonal↗
PubMed1988

Organ distribution of Adriamycin after intravesical instillation with or without Tween 80 in the rat.

The absorption of Adriamycin (ADM) into the systemic circulation and into different organs including the urinary bladder was investigated in the rat after intravesical instillation of ADM with or without a surface active detergent, Tween 80. The postinstillation plasma concentration of ADM increased significantly with increasing dose of the drug. Even though the leakage of ADM into the systemic circulation and into extravesical organs in general was slight a significant increase was observed after addition of Tween 80. The uptake of ADM into the urinary bladder wall was also significantly enhanced by Tween 80 thus the role of this agent in conjunction with intravesical chemotherapy should be further investigated.

Absorption↗
PubMed1988

Induction of CD43 expression during activation and terminal differentiation of human B cells.

Only a small population (25-30%) of human peripheral blood B lymphocytes expresses large sialoglycoprotein (LSGP) (CD43). However, in the presence of autologous T cells and pokeweed mitogen (PWM) a majority (50-90%) of the immunoglobulin-producing cells (cIg+ cells) that develop from these B cells express CD43 is detected with anti-CD43 monoclonal antibodies (MoAb) B1B6, and the proportion of CD43+cIg+ cells increases with time of culture. Furthermore, a relatively larger proportion (60-80%) of the IgG-producing cIg+ cells are CD43+ compared with IgM-containing cIg+ cells (30-50%). In human tonsils, significantly more CD43+ cells (35%) are found in the in vivo-activated fraction of B cells than in the fraction of resting B cells (5%). A majority of the cIg+ cells that develop from the resting or the in vivo-activated tonsillar B cells in a PWM-induced B-cell differentiation system are CD43+ (80-100%). Furthermore, tonsillar B cells depleted of CD43+ cells give rise to cIg+ cells, of which the majority are CD43+, and the proportion of such cells increases with time of culture (60-90%). Taken together, these results indicate that LSGP belongs to a group of B-cell membrane molecules that are induced and upregulated upon activation and differentiation.

Antigens, CD↗
PubMed1988

Characterization of human CD4+ T-cell clones that secrete helper factor(s) for B-cell proliferation and maturation.

Human peripheral blood lymphocytes (PBL) were activated with K46M, a m mitogenic monoclonal antibody against La-reactive T lymphocyte surface structures. The cultures were expanded in the presence of interleukin 2 (IL-2). After 1 month of culture, the activated T cells were cloned by limiting dilution at 0.5 cells/well. Five clones with the CD3+CD4+ phenotype and one clone with the CD3+CD8+ phenotype were obtained. The CD3+CD8+ clone (K99) displayed a strong major histocompatibility complex (MHC)-unrestricted cytolytic activity against MOLT-4 and a weaker reactivity against the bladder tumour cell lines T24 and RT4. The natural killer (NK)-susceptible K562 cells were not lysed. Two of the CD3+CD4+ clones (K91 and K914) showed a helper activity in pokeweed mitogen (PWM)-induced IgG production by B cells. These cells differed in the expression of CD45R and CDw29 antigens, as defined by the monoclonal antibodies 2H4 or D10D11 and 4B4. When stimulated with PWM for 48 or 72 h, clone K91 and an additional CD4-positive clone (K913) secreted a factor into the supernatants which helped B cells to produce IgG. The K913 supernatant also induced some IgM production. The supernatant obtained after similar stimulation of K914 cells was inactive. None of these supernatants induced B cells to proliferate when tested together with phorbol myristate acetate (PMA). However, when K91 and K914 cells were activated with phytohaemagglutinin (PHA) for 48 or 72 h, the supernatant from K91 was strongly helpful in B-cell proliferation, whereas the supernatant from K914 cultures was only moderately active. In conclusion, we have established human T helper clones that release different factors supporting either B-cell proliferation or maturation when stimulated with PWM or PHA.

Antigens, CD↗