Binding of bacteria to HEp-2 cells infected with influenza A virus

Epidemiological studies indicate influenza virus infection increases susceptibility to bacterial respiratory pathogens and to meningococcal disease. Because density of colonisation is an important factor in the development of bacterial disease, the objectives of the study were to use flow cytometry methods for assessment of bacterial binding and detection of cell surface antigens to determine: (1) if HEp-2 cells infected with human influenza A virus bind greater numbers of bacteria than uninfected cells; (2) if influenza infection alters expression of cell surface antigens which act as receptors for bacterial binding; (3) if neuraminidase affects binding of bacteria to HEp-2 cells. There was significantly increased binding of all isolates tested regardless of surface antigen characteristics. There were no significant differences between virus-infected and -uninfected Hep-2 cells in binding of monoclonal antibodies to Lewisb, Lewisx or H type 2. There were significant increases in binding of monoclonal antibodies to CD14 (P < 0.05) and CD18 (P < 0.01). Treatment of cells with monoclonal antibodies significantly reduced binding of Neisseria meningitidis strain C:2b:P1.2, CD14 (P < 0.001) and CD18 (P < 0.001). No reduction in binding of a strain of Streptococcus pneumoniae (12F) was observed in these experiments. Neuraminidase treatment of HEp-2 cells increased binding of monoclonal antibodies to CD14 (P < 0.01) and CD18 (P < 0.01). In three experiments, the increase in binding of meningococcal strain C:2b:P1.2 to neuraminidase-treated cells was not significant, but binding of Staphylococcus aureus strain NCTC 10655 was significant (P < 0.05).     

Selective colony blotting to expand bacterial surface receptors: applications to receptors for rat immunoglobulins

Many bacterial surface receptors demonstrate a heterogeneous expression pattern among individual colonies. Methods have been developed to select bacteria expressing high levels of a stable surface receptor. This process is illustrated using a Streptococcus zooepidemicus isolate demonstrating a high level of Fc receptors for rat immunoglobulins. This strain was selected and expanded to obtain a bacterial isolate demonstrating approximately 100 fold greater reactivity with rat immunoglobulins than protein A positive Staphylococcus aureus or 30-40 fold higher reactivity for rat IgG than type III Fc receptor positive streptococcal group G strains. The optimal pH for rat IgG binding and the reactivity with rat IgG subclasses and certain rat monoclonal antibodies is described. The potential application and limitations of the selected rat Fc receptor positive bacterial strain to immunoassays based on the specificity of rat monoclonal and polyclonal antibodies is discussed.     

Passive immunization to outer membrane proteins MLP and PAL does not protect mice from sepsis

Multiple older studies report that immunoglobulin directed to rough mutant bacteria, such as E. coli J5, provides broad protection against challenge with heterologous strains of Gram-negative bacteria. This protection was initially believed to occur through binding of immunoglobulin to bacterial lipopolysaccharide (LPS). However, hundreds of millions of dollars have been invested in attempting to develop clinically-effective anti-LPS monoclonal antibodies without success, and no study has shown that IgG from this antiserum binds LPS. Identification of the protective mechanism would facilitate development of broadly protective human monoclonal antibodies for treating sepsis. IgG from this antiserum binds 2 bacterial outer membrane proteins: murein lipoprotein (MLP) and peptidoglycan-associated lipoprotein (PAL). Both of these outer membrane proteins are highly conserved, have lipid domains that are anchored in the bacterial membrane, are shed from bacteria in blebs together with LPS, and activate cells through Toll-like receptor 2. Our goal in the current work was to determine if passive immunization directed to MLP and PAL protects mice from Gram-negative sepsis. Neither monoclonal nor polyclonal IgG directed to MLP or PAL conferred survival protection in 3 different models of sepsis: cecal ligation and puncture, an infected burn model, and an infected fibrin clot model mimicking peritonitis. Our results are not supportive of the hypothesis that either anti-MLP or anti-PAL IgG are the protective antibodies in the previously described anti-rough mutant bacterial antisera. These studies suggest that a different mechanism of protection is involved.     

The broad antibacterial activity of the natural antibody repertoire is due to polyreactive antibodies

Polyreactive antibodies bind to a variety of structurally unrelated antigens. The function of these antibodies, however, has remained an enigma, and because of their low binding affinity their biological relevance has been questioned. Using a panel of monoclonal polyreactive antibodies, we showed that these antibodies can bind to both Gram-negative and Gram-positive bacteria and acting through the classical complement pathway can inhibit bacterial growth by lysis, generate anaphylatoxin C5a, enhance phagocytosis, and neutralize the functional activity of endotoxin. Polyreactive antibody-enriched, but not polyreactive antibody-reduced, IgM prepared from normal human serum displays antibacterial activity similar to that of monoclonal polyreactive IgM. We conclude that polyreactive antibodies are a major contributor to the broad antibacterial activity of the natural antibody repertoire.     

The immune system response to Campylobacter infection

Campylobacter may be one of the most common causes of bacterial gastroenteritis (GE) in children. It has recently been suggested that it is one of the bacterial pathogens most likely to infect immune-compromised children, and it may facilitate colonization of enteric pathogens. The immune system response was studied in 12 children with Campylobacter fetus subspecies jejuni (CBJ) infections. Serum concentrations of IgA, IgM, and IgG were analyzed using a Beckman auto-analyzer. Sera specific Ab to CBJ were tested with CBJ specific enzyme-linked immunosorbent assay (ELISA). Mitogen stimulation of lymphocytes was performed to three lectins: Con A, PWM, and PHA. The lymphocyte blast transformation to Campylobacter was studied using the Campylobacter antigen. T-cell subsets were studied using the monoclonal antibodies Leu 2, 3, and 4 (Becton Dickinson). Chemotaxis was measured in modified Boyden chambers; chemotactic stimulants were the Formyl Met Leu Phe, Campylobacter antigen virion, and E. coli 0111 B. Immunoglobulins were normal in nine cases and abnormal in two children previously diagnosed as agammaglobulinemic and one diagnosed as hypoagammaglobulinemic. Specific serum Ab level was significantly higher in the CBJ group, except in the agammaglobulinemic group. Stimulation indices to mitogens and monoclonal subset were in the normal range. The blastogenic transformation to CBJ Ag was decreased compared to normal lectins, and positive and high compared to controls. The chemotactic activity to campylobacter Ag was decreased in comparison to other stimulants. Most CBJ infections are self-limiting due to a normal immune response and collaboration of all cellular limbs. When, however, the immune response is disturbed, we may find a prolonged and complicated course of CBJ.     

Developmental and environmental factors that enhance binding of Bordetella pertussis to human epithelial cells in relation to sudden infant death syndrome (SIDS)

Abstract Asymptomatic infection due to Bordetella pertussis has been suggested to be one cause of sudden infant death syndrome (SIDS). We examined developmental and environmental factors previously found to affect binding of another toxigenic species, Staphylococcus aureus , to human epithelial cells: expression of the Lewis^a antigen; infection with respiratory syncytial virus (RSV); exposure to cigarette smoke; and the inhibitory effect of breast milk on bacterial binding. Binding of two strains of B. pertussis (8002 and 250825) to buccal epithelial cells was significantly reduced by treating the cells with monoclonal antibodies to Lewis^a ( P < 0.05) and Lewis^x ( P < 0.01) antigens. Both strains bound in significantly greater numbers to cells from smokers compared with cells from non-smokers ( P < 0.05). HEp-2 cells infected with RSV subtypes A or B had higher binding indices for both 8002 ( P < 0.001) and 250825 ( P < 0.01). On RSV-infected cells, there was significantly enhanced binding of monoclonal antibodies to Lewis^x ( P < 0.05), CD14 ( P < 0.001) and CD18 ( P < 0.01); and pre-treatment of cells with anti-CD14 or CD18 also significantly reduced binding of both strains of B. pertussis . Pre-treatment of the bacteria with human milk significantly reduced their binding to epithelial cells. The results are discussed in relation to our three-year survey of bacterial carriage among 253 healthy infants, their mothers and local SIDS cases between 1993–1995 and in relation to the change to an earlier immunisation schedule for infants and the recent decline in SIDS in Britain.     

Production of monoclonal antibodies against Legionella pneumophila serogroup 1

Four monoclonal antibodies to Legionella pneumophila Philadelphia 1 were produced by the fusion of immunized BALB/c lymphocytes to a murine myeloma cell line. Two (Lp1-1 and Lp1-3) of the four monoclonal antibodies reacted with 14 L. pneumophila serogroup 1 strains, and the other (Lp1-2 and Lp1-4) reacted with only three out of 20 strains tested. These four monoclonal antibodies did not bind to any strains of L. pneumophila serogroup 2-7 and other Legionella species. In addition, it has been shown that these monoclonal antibodies may be useful not only for subserotyping of L. pneumophila but also for retrospective diagnosis using immunopathological methods.     

Binding of phosphorylcholine by non-immunoglobulin molecules on mouse B cells

Phosphorylcholine (PC), a molecule found in the cell wall of most serotypes of pneumococcus, has been used extensively as a probe for the study of network interactions during immune responses. The frequency of B lymphocytes capable of interacting with PC has not been directly examined. We used immunofluorescence to study the binding of PC and monoclonal anti-TEPC15 anti-idiotopic antibodies to murine lymphocytes. In addition to identifying PC-specific Ig molecules, PC was bound by a non-Ig molecule on the surface of a relatively large subset of B cells; this non-Ig marker shared an idiotypic determinant with the PC-binding myeloma protein HOPC8 (H8). PC-bearing R36a pneumococci bind to a similar subset of lymphocytes. This binding is inhibited specifically by PC coupled to bovine serum albumin and also by a monoclonal anti-H8 antibody. We suggest that bacterial interaction with B cells through non-Ig molecules capable of binding a dominant antigen like PC may possess functional significance, possibly during the events that lead to antibody induction by these microorganisms.     

The cellular basis for viral-induced immunodeficiency: analysis by monoclonal antibodies

Viral infections are often associated with immunodeficiency states. Although T lymphocytes have been thought to suppress the host's response, the precise etiology remains unclear. Therefore, we characterized T lymphocytes from six patients during both acute and convalescent phases of infectious mononucleosis (IM) with monoclonal antibodies (titer, 10(-5) to 10(-7) to antigens restricted to the TH2- helper (T4) and TH2 suppressor (T5) T cell subsets as well as to a common T cell antigen (T3) and HLA-D related Ia antigens. It was found that during acute infectious mononucleosis, there is both activation and increase of suppressor T cells (T5+, Ia+ phenotype). Fuctionally, the acute IM lymphocytes suppress autologous T cell proliferation to antigens as well as pokeweed mitogen driven B cell immunoglobulin production. In contrast, convalescence is associated with a return to normal of T cell subsets and immune function. These results demonstrate that viral infections can preferentially activate a specific T cell subset and suppress the overall human immune response.     

Circulating immature and mature dendritic cells in relation to lymphocyte subsets in patients with gastrointestinal tract cancer

Cancer-related deficiency in circulating dendritic cells (DC), whose important anticancer role is well established, has been proven to be associated with lymphocytopenia. This study was performed to evaluate which lymphocyte subset is most markedly related to the failure of the DC system. The study included 30 patients with gastrointestinal tract cancer, 10 of whom had distant organ metastases. Immature and mature DCs were measured by FACS and monoclonal antibodies against CD123 and CD11c antigens, respectively. Low levels of immature and mature DCs were observed in 63% and 43% of patients, respectively. Patients with low levels of circulating mature DCs had significantly lower values of T lymphocytes, T helper lymphocytes and NK cells than those with normal mature DC levels. In contrast, no significant difference was seen between patients with normal or abnormally low values of immature DCs. Conversely, patients with a decreased number of T lymphocytes, T helper lymphocytes and NK cells showed significantly lower values of circulating mature DCs than those with lymphocyte subsets within the normal range, whereas no difference was seen in immature DC amounts. This study suggests that only mature DC deficiency may be associated with important lymphocyte subset alterations in cancer patients, whereas deficiency in immature DCs does not seem to be related to other immune cell disorders.     

Cytochemical profile of immunoregulatory T-lymphocyte subsets defined by monoclonal antibodies

Immunogold staining in combination with enzyme cytochemistry was used to determine the cytochemical profile of the immunoregulatory T-lymphocyte subpopulations defined by the monoclonal antibodies OKT3, OKT4, OKT8, and OKM1 in normal peripheral blood. Leukocyte suspensions were first incubated with the monoclonal mouse antibodies and then with colloidal gold-labeled goat antimouse antibodies. The cells were fixed and cytocentrifuge preparations were made. Cytochemical reactions for the detection of peroxidase, acid alpha-naphthyl acetate esterase, acid phosphatase, and beta-glucuronidase were performed on these preparations. Under light microscopy, lymphocytes reacting with the monoclonal antibodies had numerous dark granules around their surface membrane. In the cytoplasm the intracellular enzymatic activities were stained. The T-lymphocytes were characterized by a dot-like activity for the three enzymes. No significant difference could be found between the cytochemical profile of the T-helper (OKT4 positive) and T-cytotoxic suppressor cell populations (OKT8 positive). A few cells with lymphocyte morphology reacted with the OKM1 monoclonal antibody. Their cytochemical characteristics were different from those of mature T-cells (OKT3 population) or mature monocytes. From the comparison of their cytochemical characteristics, we can conclude that there is little correlation between the immunoregulatory T-lymphocyte subsets defined by these monoclonal antibodies and those defined by Fc receptors.     

Murine monoclonal anti-DNA autoantibodies bind to endogenous bacteria

Several bacterial species (including Streptococcus faecalis, Bacillus cereus, Staphylococcus aureus, and Escherichia coli) were tested for their ability to react with monoclonal anti-DNA antibodies that were derived from MRL-lpr/lpr mice. S. faecalis reacted with 8/15 of such antibodies. The binding was unaffected by DNase, but it was competitively inhibited by DNA. F(ab')2 fragments of the monoclonal antibodies reacted with the bacteria, but Fc fragments did not. Phospholipids extracted from the bacterial cells were able to bind to three representative anti-DNA antibodies that also bound to whole bacteria. The results suggest that bacterial phospholipids might provide an immunogenic stimulus for the production of antibodies that cross-react with DNA. We propose that some anti-DNA auto-antibodies and anti-bacterial antibodies evolve from a restricted group of antibodies with high avidity for the phosphodiester groups that occur in DNA and bacterial cells walls.     

Differentiation capabilities of human germ cell tumors

It is well known that human germ cell tumors are an excellent model to study not only differentiation capacity of tumor cells but also human normal somatic cell differentiation. A variety of polyclonal and monoclonal antibodies were developed against cell surface antigens of murine embryos and teratocarcinomas. Accumulated data has revealed that these antigens are sequentially expressed on embryonic cells in a well-programmed manner. They have also been shown to be useful markers to investigate somatic cell differentiation in fetal and adult tissue. In humans, however, little is known about the cellular differentiation mechanism in early embryos and whether they could be studied, i.e. whether they occur in human germ cell tumors. In present review, we discussed newly established monoclonal antibodies which were raised from human embryonal carcinoma cells. We have been studying differentiation capacity of human germ cell tumor cells by using these antibodies. Some of these antibodies clearly indicates their usefulness to specify the developmental stage of normal tissue.     

Characterization of a murine monoclonal antibody specific for an allotypic determinant on T cell antigen receptor

Repeated immunization of normal C57L/J (H-2b) mice with peripheral T cells from BALB.B (H-2b) mice results in the production of antibodies which react with the T cell receptor. A monoclonal antibody-producing hybridoma, F23.1, was isolated from immunized C57L/J mice showing this property. This monoclonal antibody recognizes approximately 25% of peripheral T cells in BALB mice. It stains approximately the same fraction of T cells and precipitates the same heterodimer as the rat monoclonal antibody described previously that was made against isolated receptor material. The allotypic determinant recognized by this monoclonal antibody is present in most common laboratory strains (BALB, C57BL, CBA, A, DBA, C3H) and is absent in C57L, C57BR, and SJL mice. Sorting peripheral T cells from BALB.B or (SJL X BALB/c)F1 mice for the F23.1+ and F23.1- subsets revealed that both populations contain approximately the same CTL precursor frequency for alloantigen. Thus, the T cell receptor allotype defined by F23.1 is present on CTL. Furthermore, cytotoxicity mediated by an F23.1+ CTL line could be blocked specifically by the F23.1 monoclonal antibody. Under appropriate conditions, the monoclonal antibody F23.1 bound to Sepharose 4B beads can induce resting peripheral T lymphocytes of allotype-positive strains to proliferate.     

Importance of immunoglobulin isotype in therapy of experimental autoimmune encephalomyelitis with monoclonal anti-CD4 antibody

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease mediated by CD4+ T cells. Prior studies have established that monoclonal anti-CD4 antibodies can reverse EAE. To determine whether immunoglobulin isotype plays a role in the therapy of EAE with anti-CD4 antibody, an isotype switch variant family of the mouse IgG1 anti-rat CD4 antibody W3/25 was isolated with the fluorescence-activated cell sorter. The IgG1, IgG2b, and IgG2a W3/25 isotype variants all had identical binding capacities for rat CD4+ T cells. Although all three W3/25 isotypes showed some beneficial effects in the amelioration of EAE, the IgG1 and IgG2a W3/25 antibodies were superior to the IgG2b W3/25 in the treatment of EAE. Multiparameter fluorescence-activated cell sorter analysis of T cell subpopulations from treated rats showed that none of the antibodies of the W3/25 isotype switch variant family substantially depleted CD4+ target cells in vivo. These experiments demonstrate that immunoglobulin isotype is important in the monoclonal antibody therapy of autoimmune disease. They indicate that therapy of EAE may be successful without a major depletion of CD4+ lymphocytes. Immunotherapy may be optimized by selecting an appropriate isotype of a monoclonal antibody.     

Adherence of bacteria to human lymphocyte subpopulation and the role of monosaccharides in bacterial binding

In the present investigation lymphocyte bacterial binding, receptors for bacteria on lymphocytes, and the relationships between bacterial binding and lymphocyte activation were studied. Of the strains used Escherichia coli, Bacillus subtilis, and Corynebacterium xerosis bound to both purified T and B cells. Staphylococcus aureus, Staphylococcus albus, and Brucella melitensis bound chiefly to B lymphocytes. Monosaccharides and treatment of lymphocytes with lectins, enzymes, or sodium metaperiodate affected bacterial adherence. Thus the lymphocyte receptors for bacteria appeared to contain carbohydrate moieties. There was no clear-cut correlation between lymphocyte binding of bacteria and bacterium-induced leukocyte-inhibitory factor (LIF) synthesis and proliferation.     

Monoclonal antibodies: methods and clinical laboratory applications

Kohler and Milstein have shown that individual clones of normal antibody-secreting lymphocytes could be immortalized by fusion with myeloma cells. These investigators initiated a new era of technology with the successful in vitro production of monoclonal antibodies via somatic cell hybridization. With the use of monoclonal antibodies, many major problems arising from the limited specificity and reproducibility of conventional antisera can be solved. Some of the commonly employed methods for the production of monoclonal antibody are: (1) fusion of sensitized lymphocytes and myelomas from different sources to produce continuous antibody-producing cell lines; (2) in vitro viral transformation of sensitized lymphocytes to form continuous antibody-producing cells; (3) hybrid fusion of sensitized lymphocytes and continuous B lymphocyte cell lines. During the past few years, monoclonal antibody methodology has been used in almost every area of biological research. Monoclonal antibodies have been used as structural probes for proteins and hormones, and as highly specific agents for histocompatibility testing, tumor localization, immunotherapy, purification of molecules, identification of new surface antigens on lymphocytes and tumor cells, and detection of drug levels and microbial and parasitic diseases. In addition, several investigators have developed alternative methods for the production of human as well as mouse and rat monoclonal antibodies. The new technology of in vitro production of animal and human monoclonal antibodies will have many future applications in diagnosis and therapy in laboratory and clinical medicine.     

Increased incidence of Ia antigen-bearing T lymphocytes in the spontaneously diabetic BB rat

The frequency of Ia-positive T lymphocytes in spontaneously diabetic BB rats was assessed by using monoclonal antibodies and a fluorescence-activated cell sorter. These cells peaked in frequency during the early stages of hyperglycemia, with a gradual decline toward normal as the disease progressed. Significantly increased numbers of Ia-positive T cells were detected in both helper (W3/25+) and cytotoxic-suppressor (OX8+) subsets. The elevated levels of Ia-positive T lymphocytes in these rats may be relevant to the immune destruction of their beta cells.     

基于单个B细胞抗体基因扩增技术筛选马IgG1单克隆抗体*

在马的免疫学研究领域中,由于目前市场上缺乏商业化的马IgG单克隆抗体,使得对马的B细胞研究受到很大阻碍,IgG是B细胞受体(BCR)的重要构成成分,与B细胞分化成熟相关。为了获得马IgG特异性单克隆抗体,利用单个B细胞扩增技术进行抗体筛选。首先,将马IgG蛋白(EqIgG1-C)密码子优化后合成到真核表达载体pcDNA3.4上,纯化出抗原蛋白。随后,使用蛋白质免疫小鼠,分离脾细胞后利用流式细胞术分离特异性单个B细胞,扩增出抗体重链和轻链的可变区基因,用overlapping PCR方法扩增出线性化的完整抗体,并进行鉴定。结果从80个B细胞中获得了27株特异性重组单克隆抗体,并挑选出3株线性结合活性最强的抗体基因构建到表达载体上,共转染Expi293F^TM细胞后表达纯化,经过ELISA和Western blot验证,显示获得的抗体可以和EqIgG1-C蛋白有良好的结合作用。使用该方法可以省时高效的获得特异性抗体,为马的免疫学研究提供了重要研究工具,为鼠单克隆抗体筛选提供了技术拓展。     

Role of spleen in immune response to polyvalent pneumococcal vaccine.

The immune response of lymphocytes to subcutaneously administered pneumococcal vaccine was studied in five patients without spleens and in five healthy subjects. Seven days after immunisation circulating B cells synthesising IgG antipneumococcal capsular polysaccharides (anti-PCP) appeared in both groups. Twenty one days after vaccination this B cell population had disappeared and a B cell subset which secreted IgM and IgG anti-PCP in the presence of pokeweed mitogen was detected in the normal but not in the splenectomised subjects. In the splenectomised group polyclonal IgM synthesis induced by pokeweed mitogen was defective. It was concluded that the early events of the immune response to PCP may be mediated by lymph nodes but that, later, the spleen acquires a central role in producing lymphocyte subsets capable of synthesising specific antibodies and that this might explain the increased sensitivity of splenectomised subjects to pneumococcal infection.