Glucans as biological response modifiers

Beta-D-glucans belong to a group of natural, physiologically active compounds, generally called biological response modifiers. Glucans represent highly conserved structural components of cell walls in yeast, fungi, or seaweed. Despite long history of research, the exact mechanisms of glucan action remain unsolved. The present review starts with the history of glucans. Next, the detailed information about the possible glucan sources is followed by a description of the mechanisms of action. Physiological functions of glucan suggest the possible use of glucans not only as non-specific immunomodulator, but also as its possible future use as a drug.

Beta-glucans, history, and the present: immunomodulatory aspects and mechanisms of action

The present paper represents a comprehensive up-to-date review of beta -glucans, their chemical and biological properties, and their role in immunological reactions. beta -D-Glucans belong to a group of physiologically active compounds called biological response modifiers and represent highly conserved structural components of cell walls in yeast, fungi, or seaweed. Despite almost 150 years of research, the exact mechanisms of their action remain unclear. The present review starts with the history of glucans. Next, attention is focused on sources and structure, comparing the effects of physicochemical properties, and sources on biological effects. As glucans belong to natural products useful in preventing various diseases, they have been highly sought after throughout human history. Based on extensive recent research, this paper explains the various mechanisms of effects and the ways glucans mediate their effects on defense reactions against infections. Despite the fact that predominately pharmacological effects of glucans are positive, their unfavorable and potentially toxic side effects were not overlooked. In addition, attention was focused on the future research, possible alternatives such as synthetic oligosaccharides, and on clinical applications.

Association of the leukemia inhibitory factor gene mutation and the antiphospholipid antibodies in the peripheral blood of infertile women

To characterize the impact of the potentially functional mutation--the G to A transition at the position 3400 of the leukemia inhibitory factor (LIF; a pluripotent cytokine that plays a central role in the control of the embryo implantation) gene that leads to the exchange of valine with methionine at codon 64 we evaluated the association of the LIF gene mutation and the levels of antiphospolipid antibodies (aPLs) in the peripheral blood of infertile women (the aPLs examination was part of our routine immunological test during the infertility check-up). Eight infertile mutation-positive women were diagnosed with idiopathic infertility (n=5) and endometriosis (n=3) and their levels of aPLs in serum were compared with 115 infertile women without any LIF gene mutation. Enzyme-linked immunosorbent assay was used for the detection of seven antiphospholipid antibodies; the results were statistically assessed by the Fisher's 2 by 2 exact test to evaluate the association of the LIF gene mutations and aPLs in serum of infertile patients. The presence of aPLs was significantly higher in our study group (100%) than in 30% of aPLs-positives in control infertile patients (p = 0.0035) which indicates that the aPLs are elevated in women with LIF gene mutations.

Possible role of procathepsin D in human cancer

For the past ten years, our research has been focused on elucidating the mechanism by which procathepsin D (pCD) impacts cancer development. Various studies have shown that pCD is overexpressed and secreted by numerous cancer cell lines. After secretion, it exhibits "growth hormone-like" activity on cancerous cells but the exact mechanism of this mitogenic activity is not yet understood. The activation peptide of pCD (APpCD) (which is cleaved off upon activation of the zymogen) is responsible for the mitogenic function of pCD. Various in vitro and in vivo studies support our theory that the APpCD interacts with both parent and neighborhood cancer cells and thus functions as an autocrine mitogen. We propose a model of pCD mitogenic function and also some possible approaches for treatment and prevention of certain types of cancer.

Detection of procathepsin D in rat milk

The presence of procathepsin D, a zymogen of the soluble lysosomal aspartic proteinase cathepsin D, was detected in rat milk using Western blot analysis and assay of proteolytic activity in acidic buffers. No other forms of cathepsin D were found. Two different polyclonal anti-procathepsin D antibodies were used for immunochemical detection of procathepsin D. Both antibodies we found to recognize rat procathepsin D. Proteolytic activity in acidic buffers was detected using a fluorogenic substrate specific for cathepsin D and was abolished by pepstatin A, a specific inhibitor of aspartic proteinases. This study represents third demonstration of presence of procathepsin D in mammal breast milk. Potential sources and physiological functions are discussed.

Role of procathepsin D activation peptide in prostate cancer growth

BACKGROUND

Enzymatically inactive procathepsin D secreted from cancer cells has been confirmed to play a role in breast cancer development. We focused on prostate cancer and the role of activation peptide in mitogenic activity.

METHODS

Synthetic peptides and monoclonal antibodies raised against individual fragments of activation peptide were employed. Cell proliferation was measured by MTT (3-[4,5-dimethylthiatol-2-yl]-2,5-diphenyl tetrazolium bromide) assay or by in vivo growth in nude mice.

RESULTS

We demonstrated that the growth factor activity of activation peptide is localized in amino-acid region 27-44. In addition, both anti-activation peptide and anti-27-44 peptide antibodies administered in vivo inhibited the growth of human prostate tumors in mice.

CONCLUSIONS

Based on these data, we hypothesize that the interaction of procathepsin D activation peptide with an unknown receptor is mediated by amino-acid sequence 27-44. This interaction leads in certain types of tumor to a proliferation and higher motility. Blocking of this interaction by antibodies or antagonists might be a valuable tool in prostate cancer inhibition.

Critical role of Kupffer cell CR3 (CD11b/CD18) in the clearance of IgM-opsonized erythrocytes or soluble beta-glucan

Liver macrophages (Kupffer cells) play a major role in blood clearance of both C3-opsonized immune complexes and therapeutic beta-glucan polysaccharides. Human Kupffer cells express three types of C3-receptors: CR1 (C3b-receptor; CD35), CR3 (iC3b- and beta-glucan-receptor), and CR4 (iC3b-receptor; CD11c/CD18). Studies of isolated macrophages have suggested that CR3 is the major receptor mediating capture of either C3-opsonized erythrocytes (E) or beta-glucans. In this investigation, the organ distribution and function of CR3 in the clearance of IgM-opsonized E and soluble CR3-binding polysaccharides were explored in normal vs. CR3-knockout (CR3-KO) mice. Analysis of intravenously (i.v.) injected 125I-anti-CR3 showed that the major vascular reservoir of CR3 was the liver, followed by spleen and lungs. By contrast, clearance of 125I-anti-CR1 appeared to be mediated predominantly by splenic B lymphocytes, as only subsets of splenic macrophages or Kupffer cells were found to express CR1. Clearance of IgM-opsonized 51Cr-E occurred rapidly to the livers of normal mice but was nearly absent in CR3-KO mice. Soluble 125I-beta-glucan exhibited rapid clearance to the liver in normal mice, whereas clearance in CR3-KO mice was significantly reduced. In conclusion, Kupffer cell CR3 plays a crucial role in the clearance of both IgM-opsonized E and beta-glucans.

Anti-human procathepsin D activation peptide antibodies inhibit breast cancer development

Enzymatically inactive procathepsin D secreted from cancer cells has been confirmed to play a role in development of human breast cancer. In the present study, we focused on the role of activation peptide which was in our preliminary studies suggested to be most probably responsible for mitogenic activity of procathepsin D. Using synthetic fragments and antibodies raised against individual fragments, we demonstrated that the growth factor activity of activation peptide is localized in a nine amino acid stretch (AA 36-44) of activation peptide and moreover both anti-activation peptide and anti-27-44 peptide antibodies administered in vivo inhibited the growth of human breast tumors in athymic nude mice. Taking into account our previous results and presented data, we hypothesize that the interaction of procathepsin D activation peptide with an unknown surface receptor is mediated by a sequence 36-44 plus close vicinity. We also propose that this interaction leads in certain types of tumor derived cell lines to proliferation and higher motility. Blocking of the interaction of activation peptide by specific antibodies or antagonists might be a valuable tool in breast cancer inhibition.

Beta-glucan, a "specific" biologic response modifier that uses antibodies to target tumors for cytotoxic recognition by leukocyte complement receptor type 3 (CD11b/CD18)

beta-Glucans were identified 36 years ago as a biologic response modifier that stimulated tumor rejection. In vitro studies have shown that beta-glucans bind to a lectin domain within complement receptor type 3 (CR3; known also as Mac-1, CD11b/CD18, or alphaMbeta2-integrin, that functions as an adhesion molecule and a receptor for factor I-cleaved C3b, i.e., iC3b) resulting in the priming of this iC3b receptor for cytotoxicity of iC3b-opsonized target cells. This investigation explored mechanisms of tumor therapy with soluble beta-glucan in mice. Normal mouse sera were shown to contain low levels of Abs reactive with syngeneic or allogeneic tumor lines that activated complement, depositing C3 onto tumors. Implanted tumors became coated with IgM, IgG, and C3, and the absent C3 deposition on tumors in SCID mice was reconstituted with IgM or IgG isolated from normal sera. Therapy of mice with glucan- or mannan-rich soluble polysaccharides exhibiting high affinity for CR3 caused a 57-90% reduction in tumor weight. In young mice with lower levels of tumor-reactive Abs, the effectiveness of beta-glucan was enhanced by administration of a tumor-specific mAb, and in SCID mice, an absent response to beta-glucan was reconstituted with normal IgM or IgG. The requirement for C3 on tumors and CR3 on leukocytes was highlighted by therapy failures in C3- or CR3-deficient mice. Thus, the tumoricidal function of CR3-binding polysaccharides such as beta-glucan in vivo is defined by natural and elicited Abs that direct iC3b deposition onto neoplastic cells, making them targets for circulating leukocytes bearing polysaccharide-primed CR3. Therapy fails when tumors lack iC3b, but can be restored by tumor-specific Abs that deposit iC3b onto the tumors.

Therapeutic intervention with complement and beta-glucan in cancer

Complement (C) has two major effector systems available for host defense. The membrane attack complex (MAC) generated from components C5-C9 can form membrane-penetrating lesions that lead to cell death by causing a rapid loss of cytoplasmic components. The MAC is only effective against pathogens with outer phospholipid membranes, and cannot kill gram-positive bacteria or yeast whose membranes are protected by cell walls. The most important effector mechanism of C is the opsonization of microbial pathogens with the serum protein C3 that leads to their high avidity attachment to the C3-receptors of phagocytic cells. Pathogens that activate complement are first coated with the C3b fragment of C3, which is rapidly proteolyzed into the iC3b fragment by serum factor I. These iC3b fragments serve to promote the high avidity attachment of the 'iC3b-opsonized' pathogens to the iC3b-receptors (CR3, CD11b/CD18) of phagocytic cells and natural killer (NK) cells, stimulating phagocytosis and/or cytotoxic degranulation. Host cells, including neoplastic tumor cells, have been endowed with natural mechanisms for self-protection against both the MAC and the cytotoxic activation of CR3. This review discusses a novel type of immunotherapy for cancer that uses soluble yeast beta-glucan to override the normal resistance of iC3b-opsonized tumor cells to the cytotoxic activation of phagocyte and NK cell CR3, allowing this important effector mechanism of the C system to function against tumor cells in the same way that it normally functions against bacteria and yeast. Moreover, the cytotoxic activation of beta-glucan-primed NK cell CR3 by iC3b-opsonized tumors is shown to be accompanied by a tumor-localized secretion of the cytokines TNFalpha, IFNalpha, IFNgamma, and IL-6.

The beta-glucan-binding lectin site of mouse CR3 (CD11b/CD18) and its function in generating a primed state of the receptor that mediates cytotoxic activation in response to iC3b-opsonized target cells

Mouse leukocyte CR3 (Mac-1, alphaMbeta2 integrin) was shown to function as a receptor for beta-glucans in the same way as human CR3. Soluble zymosan polysaccharide (SZP) or pure beta-glucans labeled with FITC or 125I bound in a saturable and reversible manner to neutrophils, macrophages, and NK cells. This lectin activity was blocked by anti-CD11b mAb M1/70 or 5C6 and did not occur with leukocytes from CR3-/- (CD11b-deficient) mice. SZP preparations containing primarily mannose or glucose bound to CR3, and the binding of 125I-labeled beta-glucan to CR3 was competitively inhibited by beta-glucans from barley or seaweed, but not by yeast alpha-mannan. Also, as with human CR3, the lectin site of mouse CR3 was inhibited by alpha- or beta-methylglucoside (but not D-glucose), alpha- or beta-methylmannoside, and N-acetyl-D-glucosamine. Phagocytosis of zymosan and serum-opsonized zymosan was partially inhibited by anti-CR3 and was reduced to <40% of normal with leukocytes from CR3-/- mice. As with neutrophils from patients with CD18 deficiency, neutrophils from CR3-/- mice exhibited no phagocytosis of particulate beta-glucan. SZP or beta-glucans primed CR3 of neutrophils, macrophages, and NK cells for cytotoxicity of iC3b-opsonized tumor cells that otherwise did not trigger killing. beta-Glucan priming for cytotoxicity was inhibited by anti-CR3 and did not occur with leukocytes from CR3-/- mice. The primed state of macrophage and NK cell CR3 remained detectable for 18 to 24 h after pulsing with beta-glucans. The similarity of mouse and human CR3 in response to beta-glucans highlights the utility of mouse tumor models for development of therapeutic beta-glucans.

Effect of procathepsin D and its activation peptide on prostate cancer cells

Cathepsin D, a lysosomal aspartic proteinase, is secreted in the form of enzymatically inactive precursor in some cancer cells. This precursor, called procathepsin D, was found to exhibit growth factor activity toward breast cancer cell lines and this activity was later shown to be mediated by its activation peptide. In the present investigation we have used human procathepsin D and a synthetic 44 amino acid peptide corresponding to the activation peptide of procathepsin D to test its growth factor activity for human prostate cancer-derived cell lines PC3, DU145 and LNCaP. We have tested the level of proliferation of these cell lines depending on the presence of either procathepsin or activation peptide in the medium. In parallel, we have also measured the time dependency of this growth and established the optimal dose of activation peptide. These findings represent the first experimental data showing the direct effects of procathepsin D on prostate cancer cells.

Analysis of the interaction of procathepsin D activation peptide with breast cancer cells

Cathepsin D, a lysosomal aspartic proteinase, is secreted in the form of enzymatically inactive proenzyme by many types of human breast cancer tissue and exerts mitogenic activity toward these tissues. Flow cytometry was used to test the binding of procathepsin D purified from the secretion of the breast cancer cell line ZR-75-1 to human breast cancer cells. No previously known surface antigens or soluble M6P-R or anti-M6P-R antibodies were found to inhibit the specific binding of procathepsin D-FITC. Similarly, none of these potential inhibitors was found to inhibit growth factor activity of procathepsin D. Our results indicate that procathepsin D growth factor activity is mediated by a new, previously unknown receptor moiety and that the binding activity can be localized in position 27-44 of the activation peptide of procathepsin D. Furthermore, in vivo experiments indicate that treatment with anti-procathepsin D antibodies can reverse the growth of human breast tumors in athymic nude mice.

Targeting of natural killer cells to mammary carcinoma via naturally occurring tumor cell-bound iC3b and beta-glucan-primed CR3 (CD11b/CD18)

Previous reports have suggested that malignant cells frequently generate a humoral immune response that is ineffective in tumor destruction. Despite coating tumors with IgM and IgG that activate the C system via the classical pathway, normal membrane regulators of C (e.g., membrane cofactor protein and CD59) prevent cytotoxicity. Moreover, C3 deposition on tumors does not result in cytotoxic recognition by phagocytes or NK cells bearing C3 receptors capable of mediating destruction of C3-opsonized bacteria or yeast. The current investigation showed that freshly excised mammary tumors bore IgM, IgG, and C3 detectable by flow cytometry. Normal sera contained natural IgM and IgG Abs reactive with breast tumor cell lines, and IgG Ab titers were increased in patients with breast cancer. Breast tumor cell lines incubated in normal serum from AB+ individuals activated the classical, but not the alternative, pathway of C and became coated with C3. Despite exhibiting membrane-bound C3, serum-opsonized breast tumor cell lines were not killed by CR3 (CD11b/CD18)-bearing NK cells. Priming of NK cell CR3 with small soluble yeast beta-glucan polysaccharides enabled CR3-dependent killing of these same C3-bearing tumor cell lines. Tests of mammary carcinoma cells from freshly excised tumors demonstrated that they also bore sufficient amounts of opsonic C3 for cytotoxic recognition by NK cells bearing polysaccharide-primed CR3, whereas they were largely resistant to NK cells bearing unprimed CR3. This study demonstrates the potential utility of using naturally occurring opsonic C3 on tumor cells for specific immunotherapeutic targeting by NK cells and phagocytes bearing polysaccharide-primed CR3.

Targeting of natural killer cells to mammary carcinoma via naturally occurring tumor cell-bound iC3b and beta-glucan-primed CR3 (CD11b/CD18)

Previous reports have suggested that malignant cells frequently generate a humoral immune response that is ineffective in tumor destruction. Despite coating tumors with IgM and IgG that activate the C system via the classical pathway, normal membrane regulators of C (e.g., membrane cofactor protein and CD59) prevent cytotoxicity. Moreover, C3 deposition on tumors does not result in cytotoxic recognition by phagocytes or NK cells bearing C3 receptors capable of mediating destruction of C3-opsonized bacteria or yeast. The current investigation showed that freshly excised mammary tumors bore IgM, IgG, and C3 detectable by flow cytometry. Normal sera contained natural IgM and IgG Abs reactive with breast tumor cell lines, and IgG Ab titers were increased in patients with breast cancer. Breast tumor cell lines incubated in normal serum from AB+ individuals activated the classical, but not the alternative, pathway of C and became coated with C3. Despite exhibiting membrane-bound C3, serum-opsonized breast tumor cell lines were not killed by CR3 (CD11b/CD18)-bearing NK cells. Priming of NK cell CR3 with small soluble yeast beta-glucan polysaccharides enabled CR3-dependent killing of these same C3-bearing tumor cell lines. Tests of mammary carcinoma cells from freshly excised tumors demonstrated that they also bore sufficient amounts of opsonic C3 for cytotoxic recognition by NK cells bearing polysaccharide-primed CR3, whereas they were largely resistant to NK cells bearing unprimed CR3. This study demonstrates the potential utility of using naturally occurring opsonic C3 on tumor cells for specific immunotherapeutic targeting by NK cells and phagocytes bearing polysaccharide-primed CR3.

Soluble beta-glucan polysaccharide binding to the lectin site of neutrophil or natural killer cell complement receptor type 3 (CD11b/CD18) generates a primed state of the receptor capable of mediating cytotoxicity of iC3b-opsonized target cells

When phagocyte CR3 binds to iC3b on bacteria or yeast, phagocytosis and degranulation are triggered because of simultaneous recognition of iC3b via a CD11b I-domain binding site and specific microbial polysaccharides via a lectin site located COOH-terminal to the I-domain. By contrast, when phagocyte or natural killer (NK) cell CR3 adheres to iC3b on erythrocytes or tumor cells that lack CR3-binding membrane polysaccharides, neither lysis nor cytotoxicity are stimulated. This investigation showed that soluble CR3-specific polysaccharides such as beta-glucan induced a primed state of CR3 that could trigger killing of iC3b-target cells that were otherwise resistant to cytotoxicity. Anti-CR3 added before sugars prevented priming, whereas anti-CR3 added after sugars blocked primed CR3 attachment to iC3b-targets. Polysaccharide priming required tyrosine kinase(s) and a magnesium-dependent conformational change of the I-domain that exposed the CBRM1/5 activation epitope. Unlike LPS or cytokines, polysaccharides did not up-regulate neutrophil CR3 expression nor expose the mAb 24 reporter epitope representing the high affinity ICAM-1-binding state. The current data apparently explain the mechanism of tumoricidal beta-glucans used for immunotherapy. These polysaccharides function through binding to phagocyte or NK cell CR3, priming the receptor for cytotoxicity of neoplastic tissues that are frequently targeted with iC3b and sparing normal tissues that lack iC3b.

Function of C3 in a humoral response: iC3b/C3dg bound to an immune complex generated with natural antibody and a primary antigen promotes antigen uptake and the expression of co-stimulatory molecules by all B cells, but only stimulates immunoglobulin synthesis by antigen-specific B cells

Previous studies have shown that an optimal humoral response to a primary protein antigen requires C3 and CR2 (CD21). Sera from non-immunized donors contain natural IgM and IgG antibodies to the primary antigen keyhole limpet haemocyanin (KLH), and these have been previously shown to form immune complexes (IC) that activate the classical pathway of C, fixing iC3b/C3dg onto the KLH antigen. Such KLH IC bind to CR2 on KLH-non-specific B lymphocytes, resulting in antigen processing and MHC class II-dependent presentation to KLH-specific helper T cells. KLH IC also induce B lymphocytes to express the CD80 costimulatory molecule via simultaneous CR2 ligation with C3 and Fc gammaRII (CD32) stimulation by IgG natural antibody. The current study demonstrated that KLH IC ligation to either CR2 or Fc gammaRII resulted in activation of a second co-stimulatory molecule, LFA-1 (CD11a, CD18). The possibility of polyclonal B cell stimulation by the presentation of KLH-iC3b/C3dg by antigen-non-specific B cells was excluded by demonstration that in vitro cultivation of peripheral blood mononuclear cells (PBMC) with KLH-iC3b/C3dg elicited only anti-KLH, and did not stimulate synthesis of antibodies to hepatitis C virus (HCV) or tetanus toxoid (TT). Of greatest significance, a specific anti-KLH response was only detectable in cultures stimulated with KLH-iC3b/C3dg and not in cultures stimulated with KLH alone or KLH-IgG. Thus, iC3b/C3dg that was bound to a primary protein antigen enhanced recognition and specific immunoglobulin synthesis by antigen-specific B cells, even though the antigen was taken up and processed via CR2 by both antigen-specific and non-specific B cells.

Human procathepsin D: three-dimensional model and isolation

Human procathepsin D was isolated from medium of human breast cancer cell line ZR-75-1 potentiated with estrogen. The isolation involved both immunoaffinity chromatography and ion-exchange chromatography. The affinity chromatography employed polyclonal antibodies raised against a synthetic activation peptide of human cathepsin D. We have started preliminary crystallization trials using the isolated material. A model of human procathepsin D was also built using coordinates of human cathepsin D and pig pepsinogen. The model aids understanding of multiple roles played by activation peptides of aspartic proteinases and will be used as a starting model for molecular replacement.

Mitogenic function of human procathepsin D: the role of the propeptide

The proform of cathepsin D is secreted by some human breast-cancer cell lines upon stimulation with oestrogen. In these cell lines, procathepsin D was described to act as an autocrine mitogen, and a correlation between the cathepsin D concentration in tumour tissues and poor prognosis for the patient was demonstrated in several independent investigations. In the present study, we focused on the mechanism of procathepsin D mitogenic activity. Procathepsin D isolated from secretions of ZR-75-1 breast-cancer cell line was used to test for mitogenic activity on a set of seven human cell lines. For nanomolar procathepsin D concentrations, we found a stronger dose-responsive cellular reaction in the case of several different human breast-cancer-derived cell lines. The mitogenic activity was not blocked by the inhibition of proteolytic activity nor by the inhibition of the interaction of procathepsin D with mannose-6-phosphate receptors. On the other hand, the addition of antibodies raised against the propeptide impaired the mitogenic activity of procathepsin D, and a synthetic peptide alone corresponding to the propeptide of procathepsin D produced similar effects, as did the zymogen molecule. The synthetic propeptide was shown to block partially the interaction of procathepsin D with the cellular surface. Our results indicate that the mitogenic function involves the propeptide of cathepsin D, which appears to be recognized by a surface receptor.

Effect of age on antibody responses in low responder C57BL/10ScSn and high responder A/J strains of mice

The IgM antibody response to sheep red blood cells (SRBC) appeared significantly earlier in A/J strain mice (already in 10-day-old animals), but after 21 days responses were higher in B10 mice. These differences disappeared after reaching adulthood and IgM responses after either primary or secondary immunization were thereafter comparable in these strains. High-responder A/J mice made significantly more IgG antibodies than low-responder B10 mice from 21 days of age and strong differences lasted until the age of 19 months, when IgG antibody production was again similar. Potentiation of IgM formation by simultaneous application of 10 micrograms of LPS was higher in B10 mice until 19 months of age. On the other hand, potentiation of the IgG response was markedly high in B10 mice only in adult animals (3 months). Thereafter the potentiation was higher in A/J mice. The onset of Ig secretion in A/J mice was at 15 days and markedly increased at the age of 30 days. Levels of immunoglobulin synthesis remained extremely low in B10 mice. Age-related changes in IgG antibody production generally correlated with the decline of MHC class II antigen expression on peritoneal macrophages in these strains.

Effect of ambient temperature on immune functions of athymic nude mice

We performed cytoflourometric analysis of the expression of various T and B surface markers on lymphocytes isolated from bone marrow, spleen and lymph nodes of nu/nu and +/+ mice kept at 22 or 28 degrees C for various time intervals. In bone marrow of nu/nu mice the cold exposure decreased the expression of sIg and CD4 molecules and increased expression of MHC class II antigens. In the spleen, the numbers of MHC class II and sIg expressing lymphocytes continually decreased with the length of cold exposure. At the same time, the number of CD4+ cells increased. The most pronounced changes in lymph nodes were observed in the expression of CD5 antigen. The values obtained from euthymic mice kept at cold temperature were always comparable to those found in mice kept at 28 degrees C. Exposure to lowered temperature caused in nu/nu mice also significant changes in appearance of subpopulations of cells differing in size and in density of antigens. The changes did not affect the antibody response to a thymus-independent antigen.

Effect of ambient temperature on phenotype and functions of professional phagocytes of athymic nude mice

Cytofluorometric analysis of surface marker expression was performed on myeloid cells isolated from bone marrow, spleen and lymph nodes of nude mice and nu/+ and +/+ mice (haired controls) exposed for various time periods to ambient temperature of 22 degrees C or 28 degrees C. A rise in the proportion of cells bearing macrophage markers (MAC-1, MAC-3 and F4/80) in the spleen and of FcR+ cells in all tissues tested was found in 22 degrees C-exposed nudes with high nonshivering thermogenesis. Numbers of MAC-1+ macrophages and actively phagocytic cells increased also in peritoneal exudates. There was a conspicuous predominance of large macrophages in the exudates and the specific markers decreased in density on their surface. Ia expression declined in all tissues tested with the length of exposure to cold. In the granulocytic series (BP-2+ cells), there was a decrease in the bone marrow and lymph nodes and an increase in the spleen and circulation, which suggested an enhanced mobilization and increased production at extramedullary sites in cold-exposed nude mice. The changes in haired mice were negligible.

In vitro antigen-binding properties of coelomocytes of Eisenia foetida (Annelida)

Annelids are capable of cellular and humoral defence reactions against foreign antigens. The main aim of this study was to characterise the antigen-binding properties of coelomocytes of Eisenia foetida by means of quantitative autoradiography and direct measurement of radioactivity. It was found that the antigen-binding capacity was significantly increased after antigen stimulation. Furthermore, the preincubation of coelomocytes with non-labelled proteins reduced the binding of radiolabelled antigen. The highest level of inhibition was found when the same protein was used for preincubation. These results indicate that antigen-binding properties are to some extent specific.

Biocompatibility of N-(2-hydroxypropyl) methacrylamide copolymers containing adriamycin. Immunogenicity, and effect on haematopoietic stem cells in bone marrow in vivo and mouse splenocytes and human peripheral blood lymphocytes in vitro

N-(2-hydroxypropyl)methacrylamide polymeric prodrugs containing adriamycin bound to polymers via glycylphenylalanylleucylglycine side chains and, in one case, galactosamine bound via the same sequence, were tested for immunogenicity after intravenous, subcutaneous and oral application in two inbred strains of mice. The serum antibody level was determined by enzyme-linked immunoassay on the 3rd and 6th day after the last treatment. It was found that antibodies were only produced in very small amounts. In some experimental groups, the antibody titres measured following administration of copolymer conjugate were comparable with those present in non-treated controls. Attachment of adriamycin to N-(2-hydroxypropyl)methacrylamide copolymer considerably decreased its toxicity against haematopoietic precursors in bone marrow as measured by the in vivo colony-forming unit-spleen assay and its ability to inhibit [3H] thymidine incorporation by mouse splenocytes and human peripheral blood lymphocytes measured in vitro.

The effects of 5-fluorouracil on immunocompetent cells depend on the genotype of experimental animals used

A detailed study was made of the effects of 5-fluorouracil (5-FU) on primary and secondary immune responses to a T-dependent antigen in mice. Subcutaneous, intraperitoneal and intravenous applications gave similar results, oral administration was less effective. The minimal effective dose was found to be 40 mg/kg. Inbred strains known to differ in terms of IgG immune responses were compared and found to respond quite differently to the drug. For example, when 5-FU was injected 24 h before or simultaneously with antigen, IgM plaque-forming cell (PFC) responses of C57BL/10 mice were not substantially affected. In contrast, responses of A/J and Balb/c mice were suppressed 50-90% under the same conditions. If injected 24 h after the antigen, 5-FU inhibited PFC responses completely in all three strains. IgM PFC recovery was fastest in the C57BL/10 strain and started on day 7. In secondary responses, IgM overstimulation was seen in C57BL/10 and Balb/c mice if 5-FU was injected once, i.e. 24 h after primary immunization. IgG PFC were completely suppressed in primary responses in all strains. In secondary responses, the decrease was influenced by the time of drug injection and by the genotype of the treated animal. Inhibition of isotype switching was greatest in low-IgG-responding C57BL/10 mice. These results demonstrate that genotypic variation can be substantial with respect to effects of 5-FU on the immune system.

Effects of 5-fluorouracil on B lymphocyte lineage cells

The aim of these studies was to determine the sensitivity of B lymphocyte lineage precursor cells in mice to 5-fluorouracil (5-FU). Selective effects could be very helpful in dissecting precursor-product relationships between these and the rare multipotential stem cells from which they derive. Numbers and functions of particular types of cells were determined at intervals after a single treatment (3 mg) and, as expected, myeloid-committed stem cells were very severely affected. Day 8 spleen colony-forming cells (CFU-S) and colony-stimulating factor-responsive macrophage progenitors were reduced by 98% within 24 hr, whereas presumptive early stem cells (day 14 CFU-S) were much more resistant. B cells, which were probably recently formed in bone marrow and which are not thought to be actively dividing, were also 5-FU-sensitive, but perhaps less so than pre-B cells and immunoglobulin-negative lymphocytes bearing a B lineage marker. Approximately 5 wk were required for the normal cellular composition of marrow to return to normal. Transplantation of marrow from 5-FU-treated mice suggested that the slow regeneration of B lymphocytes might partially result from residual drug effects or damage to microenvironmental elements which are required for B lineage differentiation. Acute reductions of lymphocytes in the thymus were also documented, and the larger cells declined most rapidly and regenerated most slowly in that tissue. Of particular interest was the differential susceptibility of B cells in various lymphoid tissues to 5-FU. Whereas lymph node B cells were minimally affected, one-half of the splenic B cells disappeared within 48 hr of drug injection. Intrinsic differences in 5-FU sensitivity were confirmed by treatment of lymphocytes in vitro, and this suggests that particular B cell sets may be metabolically distinct. This drug should find additional experimental application in studies of B lymphocyte formation and functional heterogeneity.

Effects of 5-fluorouracil on B lymphocyte lineage cells

The aim of these studies was to determine the sensitivity of B lymphocyte lineage precursor cells in mice to 5-fluorouracil (5-FU). Selective effects could be very helpful in dissecting precursor-product relationships between these and the rare multipotential stem cells from which they derive. Numbers and functions of particular types of cells were determined at intervals after a single treatment (3 mg) and, as expected, myeloid-committed stem cells were very severely affected. Day 8 spleen colony-forming cells (CFU-S) and colony-stimulating factor-responsive macrophage progenitors were reduced by 98% within 24 hr, whereas presumptive early stem cells (day 14 CFU-S) were much more resistant. B cells, which were probably recently formed in bone marrow and which are not thought to be actively dividing, were also 5-FU-sensitive, but perhaps less so than pre-B cells and immunoglobulin-negative lymphocytes bearing a B lineage marker. Approximately 5 wk were required for the normal cellular composition of marrow to return to normal. Transplantation of marrow from 5-FU-treated mice suggested that the slow regeneration of B lymphocytes might partially result from residual drug effects or damage to microenvironmental elements which are required for B lineage differentiation. Acute reductions of lymphocytes in the thymus were also documented, and the larger cells declined most rapidly and regenerated most slowly in that tissue. Of particular interest was the differential susceptibility of B cells in various lymphoid tissues to 5-FU. Whereas lymph node B cells were minimally affected, one-half of the splenic B cells disappeared within 48 hr of drug injection. Intrinsic differences in 5-FU sensitivity were confirmed by treatment of lymphocytes in vitro, and this suggests that particular B cell sets may be metabolically distinct. This drug should find additional experimental application in studies of B lymphocyte formation and functional heterogeneity.

Biochemical characterization of Fc gamma receptors of mouse DCH-5 cell line

Fc gamma receptors (Fc gamma R) were isolated from the culture medium of a mouse hybrid cell line (DCH-5) known as an over-expressor of Fc gamma R, established from a mouse adherent spleen cell and the thymoma cell BW 5147. Proteins adsorbed to insolubilized IgG were separated on Sephacryl S-200. The main fraction with maximum FcR activity was isolated and characterized as a glycoprotein with an effective molar mass of about 55 kg/mol. Under non-denaturing conditions, the protein existed as a non-covalently linked dimer. Isoelectric focussing in agarose gel showed two bands with pI = 5.2 and pI = 5.3. The amino acid composition of this fraction was similar to that of pig and human Fc gamma R, and also of rabbit FcR for polymeric Ig. The sugar composition of the fraction (about 34% w/w) resembled that of the C1q component of complement and some membrane glycoproteins.

Intrinsic B lymphocyte and macrophage defects in C3H/HeJ mice

C3H/HeJ mice are genetically defective in their responsiveness to lipopolysaccharide (LPS). Their B cells also have a characteristically low cloning efficiency in semisolid agar cultures, where LPS does not seem to be required. Adherent macrophages facilitate clonal proliferation in such cultures via diffusible substances. C3H/HeJ macrophages functioned poorly in this respect, and addition of normal C3HeB/FeJ macrophages to cultures of C3H/HeJ B cells did not lead to normal colony numbers. Although immune interferon can stimulate normal resident peritoneal macrophages to function well in semisolid agar cultures, it did not improve the cloning efficiency of C3H/HeJ cells. Similarly, addition of indomethacin or interleukin 1 to the cultures did not reveal that abnormally elevated production of prostaglandins or a deficiency in interleukin 1 are responsible for poor C3H/HeJ colony formation. These results indicate that C3H/HeJ mice have defects intrinsic to both B cells and macrophages that are not overcome by interferon. Purified B cells from these mice cloned poorly and did not respond to stimulation in liquid cultures with anti-mu-coated beads plus factors. There was a tendency for the poor cloning of C3H/HeJ B cells to improve with age.

Intrinsic B lymphocyte and macrophage defects in C3H/HeJ mice

C3H/HeJ mice are genetically defective in their responsiveness to lipopolysaccharide (LPS). Their B cells also have a characteristically low cloning efficiency in semisolid agar cultures, where LPS does not seem to be required. Adherent macrophages facilitate clonal proliferation in such cultures via diffusible substances. C3H/HeJ macrophages functioned poorly in this respect, and addition of normal C3HeB/FeJ macrophages to cultures of C3H/HeJ B cells did not lead to normal colony numbers. Although immune interferon can stimulate normal resident peritoneal macrophages to function well in semisolid agar cultures, it did not improve the cloning efficiency of C3H/HeJ cells. Similarly, addition of indomethacin or interleukin 1 to the cultures did not reveal that abnormally elevated production of prostaglandins or a deficiency in interleukin 1 are responsible for poor C3H/HeJ colony formation. These results indicate that C3H/HeJ mice have defects intrinsic to both B cells and macrophages that are not overcome by interferon. Purified B cells from these mice cloned poorly and did not respond to stimulation in liquid cultures with anti-mu-coated beads plus factors. There was a tendency for the poor cloning of C3H/HeJ B cells to improve with age.