T cells activated by zwitterionic molecules prevent abscesses induced by pathogenic bacteria

Immunologic paradigms classify bacterial polysaccharides as T cell-independent antigens. However, these models fail to explain how zwitterionic polysaccharides (Zps) confer protection against intraabdominal abscess formation in a T cell-dependent manner. Here, we demonstrate that Zps elicit a potent CD4+ T cell response in vitro that requires available major histocompatibility complex class II molecules on antigen-presenting cells. Specific chemical modifications to Zps show that: 1) the activity is specific for carbohydrate structure, and 2) the proliferative response depends upon free amino and carboxyl groups on the repeating units of these polysaccharides. Peptides synthesized to mimic the zwitterionic charge motif associated with Zps also exhibited these biologic properties. Lysine-aspartic acid (KD) peptides with more than 15 repeating units stimulated CD4+ T cells in vitro and conferred protection against abscesses induced by bacteria such as Bacteroides fragilis and Staphylococcus aureus. Evidence for the biologic importance of T cell activation by these zwitterionic polymers was provided when human CD4+ T cells stimulated with these molecules in vitro and adoptively transferred to rats in vivo conferred protection against intraabdominal abscesses induced by viable bacterial challenge. These studies demonstrate that bacterial polysaccharides with a distinct charge motif activate T cells and that this activity confers immunity to a distinct pathologic response to bacterial infection.     

A unique structural pattern shared by T-cell-activating and abscess-regulating zwitterionic polysaccharides

In contrast to the conventional dogma that carbohydrates are poorly immunogenic T-cell-independent antigens, zwitterionic polysaccharides (ZPSs) can significantly stimulate T-cell proliferation and regulate abscess formation in bacterial infection. Despite their similar biological activities, ZPSs from various bacteria are greatly different in primary chemical compositions and building block linkages. To identify the common structural features that govern the peculiar immunologic activity of ZPSs, we have been determining three-dimensional structures of compositionally different ZPSs by NMR spectroscopy and molecular mechanics and dynamics calculations. We report here the conformation of type 1 capsular polysaccharide from the human pathogen Streptococcus pneumoniae (Sp1) to be a right-handed helix with repeated zwitterionically charged grooves. We also report the striking similarity between the structures of Sp1 and our previously determined PS A2 from Bacteroides fragilis. These results support our hypothesis that T-cell-activating ZPSs assume similar conformational and charge patterns that are recognized by specific receptors and that account for their common property as T-cell activators.     

Biological chemistry of immunomodulation by zwitterionic polysaccharides

Capsular polysaccharides isolated from pathogenic bacteria are comprised typically of many repeating units from one to eight or more monosaccharides in length. These polysaccharides stimulate the murine humoral immune system to elicit primarily IgM antibody responses. Studies conducted primarily in the mouse have characterized these polymers as T cell-independent antigens. These mouse studies and the relatively poor immunogenicity of polysaccharides in human hosts have led to the design of vaccines by coupling these polysaccharides to protein carriers to stimulate a T cell-dependent response. However, a newly described class of bacterial polysaccharides has been characterized that have the ability to modulate the cellular immune system. They are structurally diverse, but all share a zwitterionic charge motif that allows them to directly interact with T cells and antigen-presenting cells to initiate an immunomodulatory T cell response. These polymers, termed zwitterionic polysaccharides (ZPSs), elicit T cell-derived chemokines and cytokines that influence the immune response governing at least one classic host response to bacterial infection: abscess formation. This review will describe the biological and structural aspects of ZPSs that convey these activities.     

Enhanced immune responses in transgenic mice expressing a truncated form of the lymphocyte semaphorin CD100

CD100/Sema4D is a 150-kDa transmembrane protein that belongs to the semaphorin family. Binding of CD100 to CD72 enhances the immune response by turning off the negative signaling effects of CD72. To investigate the physiological functions of CD100 in vivo, we generated transgenic mice expressing a truncated form of CD100. A large amount of the soluble form of CD100 was detected in the sera of mice expressing a truncated form of CD100, although the amount of CD100 was only slightly elevated on the surface of B cells. In the mutant mice the development of conventional B and T cells appeared normal in terms of the surface marker phenotypes, while the number of CD5(+) B-1 cells in the peritoneal cavity increased in comparison with wild-type mice. In vitro proliferation and Ig production of B cells in response to CD40 stimulation were considerably enhanced in mice expressing a truncated form of CD100. Additionally, in vivo both Ab responses against T cell-dependent Ags and generation of Ag-specific T cells were enhanced. Furthermore, introduction of the CD100-transgene could restore in vitro B cell responses as well as in vivo Ab production against T cell-dependent Ag in CD100-deficient mice. Collectively, these results not only indicate that CD100 has an important role in the immune system, but also that the soluble form of CD100 released from the cell surface can exert functions in vivo.     

Induction in mice of cell-mediated immunity to Pseudomonas aeruginosa by high molecular weight polysaccharide and vinblastine

The effect of the cytotoxic drug vinblastine on the development of immunity to high m.w. polysaccharide (PS) isolated from culture supernates of Pseudomonas aeruginosa was investigated. One microgram of PS, a normally nonimmunogenic, nonprotective dose, plus 75 micrograms of vinblastine were administered to BALB/c mice, and afforded protection to live organism challenge with the homologous strain. The kinetics and serotype specificity of the immune response indicated an active immunization had occurred. Analyses of serum antibody levels of mice given the PS-drug regimen in a sensitive, radioactive antigen-binding assay (RABA) failed to show development of antibody to the immunizing PS. Immunity could be passively transferred with spleen cells but not by serum from PS-drug-immunized animals, and the effector cell was removed by antisera to the Thy-1.2 antigen. Nu/nu mice were also protected against challenge after immunization with PS and vinblastine, but this protection was observed in association with the development of serum antibody to PS in these mice, as measured in the RABA. Protective immunity could not be elicited in the BALB/c mice by PS plus cyclophosphamide. These data suggest that under certain conditions, PS antigens can elicit T cell-dependent immune phenomena, and this T cell-dependent immunity can protect mice from live organism challenge against an extracellular bacterial pathogen.     

Structural characterization and MHCII-dependent immunological properties of the zwitterionic O-chain antigen of Morganella morganii

Morganella morganii is a commensal Gram-negative bacterium that has long been known to produce an antigen bearing phosphocholine groups. We determined the structure of this O-chain antigen and found that its repeating unit also contains a free amino group and a second phosphate: This alternating charge character places the M. morganii O-chain polysaccharide into a small family of zwitterionic polysaccharides (ZPSs) known to induce T-cell-dependent immune responses via presentation by class II major histocompatibility complex (MHCII) molecules. In vitro binding assays demonstrate that this O-chain interacts with MHCII in a manner that competes with binding of the prototypical ZPS antigen PSA from Bacteroides fragilis, despite its lack of a helical structure. Cellular studies also showed that the M. morganii polysaccharide induces activation of CD4(+) T-cells. Antibody binding experiments using acid hydrolyzed fragments representing the monomer and higher oligomers of the repeating unit showed that the phosphocholine group was the dominant element of the epitope with an overall affinity (K(D)) of about 5 × 10(-5) M, a typical value for an IgM anti-carbohydrate antibody but much lower than the affinity for phosphocholine itself. These data show that the structure of the M. morganii polysaccharide contains a unique zwitterionic repeating unit which allows for immune recognition by T-cells, making it the first identified T-cell-dependent O-chain antigen.     

The capsular polysaccharide of Bacteroides fragilis comprises two ionically linked polysaccharides.

Recently, we have shown that the capsular polysaccharide of Bacteroides fragilis NCTC 9343 is composed of an aggregate of two discrete large molecular weight polysaccharides (designated polysaccharides A and B). Following disaggregation of this capsular complex by very mild acid treatment, high resolution NMR spectroscopy demonstrated that polysaccharides A and B consist of highly charged repeating unit structures with unusual substituent groups (Baumann, H., Tzianabos, A. O., Brisson, J.-R., Kasper, D.L., and Jennings, H.J. (1992) Biochemistry 31, 4081-4089). Presently, we report that the capsular polysaccharide of B. fragilis represents a complex structure that is formed as a result of ionic interactions between polysaccharides A and B. Electron microscopy of immunogold-labeled organisms (with monoclonal antibodies specific for polysaccharides A and B) demonstrated that the two polysaccharides are co-expressed on the cell surface of B. fragilis. We have shown that the purified capsule complex is made up exclusively of polysaccharide A and polysaccharide B (no other macromolecular structure was detected) in a 1:3.3 ratio and that disaggregation of this complex into the native forms of the constituent polysaccharides could be accomplished by preparative isoelectric focusing. Structural analyses of the native polysaccharides A and B showed that they possessed the same repeating unit structures as the respective acid-derived polysaccharides. The ionic nature of the linkage between polysaccharides A and B was demonstrated by reassociation of the native polysaccharides to form an aggregated polymer comparable to the original complex. The distinctive composition of this macromolecule may provide a rationale for the unusual biologic properties associated with the B. fragilis capsular polysaccharide.     

Characteristics of carbohydrate antigen binding to the presentation protein HLA-DR

Zwitterionic polysaccharide antigens (ZPSs) were recently shown to activate T cells in a class II major histocompatibility complex (MHCII)-dependent fashion requiring antigen presenting cell (APC)-mediated oxidative processing although little is known about the mechanism or affinity of carbohydrate presentation (Cobb BA, Wang Q, Tzianabos AO, Kasper DL. 2004. Polysaccharide processing and presentation by the MHCII pathway. Cell. 117:677-687). A recent study showed that the helical conformation of ZPSs (Wang Y, Kalka-Moll WM, Roehrl MH, Kasper DL. 2000. Structural basis of the abscess-modulating polysaccharide A2 from Bacteroides fragilis. Proc Natl Acad Sci USA. 97:13478-13483; Choi YH, Roehrl MH, Kasper DL, Wang JY. 2002. A unique structural pattern shared by T-cell-activating and abscess-regulating zwitterionic polysaccharides. Biochemistry. 41:15144-15151) is closely linked with immunogenic activity (Tzianabos AO, Onderdonk AB, Rosner B, Cisneros RL, Kasper DL. 1993. Structural features of polysaccharides that induce intra-abdominal abscesses. Science. 262:416-419) and is stabilized by a zwitterionic charge motif (Kreisman LS, Friedman JH, Neaga A, Cobb BA. 2007. Structure and function relations with a T-cell-activating polysaccharide antigen using circular dichroism. Glycobiology. 17:46-55), suggesting a strong carbohydrate structure-function relationship. In this study, we show that PSA, the ZPS from Bacteroides fragilis, associates with MHCII at high affinity and 1:1 stoichiometry through a mechanism mirroring peptide presentation. Interestingly, PSA binding was mutually exclusive with common MHCII antigens and showed significant allelic differences in binding affinity. The antigen exchange factor HLA-DM that catalyzes peptide antigen association with MHCII also increased the rate of ZPS association and was required for APC presentation and ZPS-mediated T cell activation. Finally, the zwitterionic nature of these antigens was required only for MHCII binding, and not endocytosis, processing, or vesicular trafficking to MHCII-containing vesicles. This report is the first quantitative analysis of the binding mechanism of carbohydrate antigens with MHCII and leads to a novel model for nontraditional MHCII antigen presentation during bacterial infections.     

Transport of Streptococcus pneumoniae capsular polysaccharide in MHC Class II tubules

Bacterial capsular polysaccharides are virulence factors and are considered T cell-independent antigens. However, the capsular polysaccharide Sp1 from Streptococcus pneumoniae serotype 1 has been shown to activate CD4(+) T cells in a major histocompatibility complex (MHC) class II-dependent manner. The mechanism of carbohydrate presentation to CD4(+) T cells is unknown. We show in live murine dendritic cells (DCs) that Sp1 translocates from lysosomal compartments to the plasma membrane in MHCII-positive tubules. Sp1 cell surface presentation results in reduction of self-peptide presentation without alteration of the MHCII self peptide repertoire. In DM-deficient mice, retrograde transport of Sp1/MHCII complexes resulting in T cell-dependent immune responses to the polysaccharide in vitro and in vivo is significantly reduced. The results demonstrate the capacity of a bacterial capsular polysaccharide antigen to use DC tubules as a vehicle for its transport as an MHCII/saccharide complex to the cell surface for the induction of T cell activation. Furthermore, retrograde transport requires the functional role of DM in self peptide-carbohydrate exchange. These observations open new opportunities for the design of vaccines against microbial encapsulated pathogens.     

Antibody production in vitamin A-depleted rats is impaired after immunization with bacterial polysaccharide or protein antigens

Vitamin A nutritional status has been implicated as important in maintaining the integrity of immune functions. We have determined the effect of vitamin A (retinol) depletion on the ability of young animals to produce antibodies after challenge with various bacterial antigens. Male Lewis rats raised on vitamin A-free or adequate diets were immunized either near 40 days of age, before signs of vitamin A deficiency were apparent, or near 47 days of age when symptoms of deficiency were beginning to be manifest. For rats immunized with polysaccharide antigens from Streptococcus pneumoniae or Neisseria meningitidis, antibody production did not exceed 0-19% of the response of control rats. Vitamin A depletion also severely compromised the response to two T cell-dependent antigens, tetanus toxoid and sheep red blood cells. In striking contrast, retinol-depleted rats immunized with lipopolysaccharides from Pseudomonas aeruginosa and Serratia marcesens produced an antibody response indistinguishable from retinol-sufficient animals. These lipopolysaccharides could elicit antibodies in rat pups, whereas the capsular polysaccharide antigens could not. This is consistent with the characteristics of type 1 and type 2 antigens, respectively. These studies indicate that retinol status is an important determinant of the humoral immune response to certain types of antigen and suggest that antibody production to capsular polysaccharides and T cell-dependent antigens is particularly dependent on adequate retinol status.     

Zwitterionic polysaccharides stimulate T cells by MHC class II-dependent interactions

Polysaccharides of pathogenic extracellular bacteria commonly have negatively charged groups or no charged groups at all. These molecules have been considered classic T cell-independent Ags that do not elicit cell-mediated immune responses in mice. However, bacterial polysaccharides with a zwitterionic charge motif (ZPSs), such as the capsular polysaccharides of many strains of Bacteroides fragilis, Staphylococcus aureus, and Streptococcus pneumoniae type 1 elicit potent CD4(+) T cell responses in vivo and in vitro. The cell-mediated response to ZPS depends on the presence of both positively charged and negatively charged groups on each repeating unit of the polysaccharide. In this study, we define some of the requirements for the presentation of ZPS to CD4(+) T cells. We provide evidence that direct interactions of T cells with APCs are essential for T cell activation by ZPS. Monocytes, dendritic cells, and B cells are all able to serve as APCs for ZPS-mediated T cell activation. APCs lacking MHC class II molecules do not support this activity. Furthermore, mAb to HLA-DR specifically blocks ZPS-mediated T cell activation, while mAbs to other MHC class II and class I molecules do not. Immunoprecipitation of lysates of MHC class II-expressing cells following incubation with ZPS shows binding of ZPS and HLA-DR. Electron microscopy reveals colocalization of ZPS with HLA-DR on the cell surface and in compartments of the endocytic pathway. These results indicate that MHC class II molecules expressing HLA-DR on professional APCs are required for ZPS-induced T cell activation. The implication is that binding of ZPS to HLA-DR may be required for T cell activation.     

The zwitterionic cell wall teichoic acid of Staphylococcus aureus provokes skin abscesses in mice by a novel CD4+ T-cell-dependent mechanism

Zwitterionic polysaccharide (ZPS) components of the bacterial cell envelope have been shown to exert a major histocompatibility complex (MHC) II-dependent activation of CD4+ T cells, which in turn can modulate the outcome and progression of infections in animal models. We investigated the impact of zwitterionic cell wall teichoic acid (WTA) produced by Staphylococcus aureus on the development of skin abscesses in a mouse model. We also compared the relative biological activities of WTA and capsular polysaccharide (CP), important S. aureus pathogenicity factors, in abscess formation. Expression of both WTA and CP markedly affected the ability of S. aureus to induce skin abscess formation in mice. Purified wild-type zwitterionic WTA was more active in inducing abscess formation than negatively charged mutant WTA or purified CP8. To assess the ability of purified native WTA to stimulate T cell proliferation in vitro, we co-cultivated WTA with human T-cells and antigen presenting cells in the presence and absence of various inhibitors of MHC-II presentation. Wild-type WTA induced T cell proliferation to a significantly greater extent than negatively charged WTA. T cell activation was dependent on the presentation of WTA on MHC II, since inhibitors of MHC II-dependent presentation and antibodies to MHC II significantly reduced T cell proliferation. T cells activated in vitro with wild-type WTA, but not negatively charged WTA, induced abscess formation when injected subcutaneously into wild-type mice. CD4-/- mice similarly injected with WTA failed to develop abscesses. Our results demonstrate that the zwitterionic WTA of S. aureus induces CD4+ T-cell proliferation in an MHCII-dependent manner, which in turn modulates abscess formation in a mouse skin infection model. An understanding of this novel T cell-dependent host response to staphylococcal abscess formation may lead to the development of new strategies to combat S. aureus skin and soft tissue infections.     

Polysaccharide A from the Capsule of Bacteroides fragilis Induces Clonal CD4+ T Cell Expansion

For 3 decades, the view of MHCII-dependent antigen presentation has been completely dominated by peptide antigens despite our 2004 discovery in which MHCII was shown to present processed fragments of zwitterionic capsular polysaccharides to T cells. Published findings further demonstrate that polysaccharide A (PSA) from the capsule of Bacteroides fragilis is a potent activator of CD4⁺ T cells and that these T cells have important biological functions, especially in the maintenance of immunological homeostasis. However, little is known about the nature of T cell recognition of the polysaccharide-MHCII complex or the phenotype of the resulting activated cells. Here, we use next-generation sequencing of the αβT cell receptor of CD4⁺ T cells from mice stimulated with PSA in comparison with protein antigen simulation and non-immunized controls and found that PSA immunization induced clonal expansion of a small subset of suppressive CD4⁺CD45RB^low effector/memory T cells. Moreover, the sequences of the complementarity-determining region 3 (CDR3) loop from top clones indicate a lack of specific variable β and joining region use and average CDR3 loop length. There was also a preference for a zwitterionic motif within the CDR3 loop sequences, aligning well with the known requirement for a similar motif within PSA to enable T cell activation. These data support a model in which PSA, and possibly other T cell-dependent polysaccharide antigens, elicits a clonal and therefore specific CD4⁺ T cell response often characterized by pairing dual-charged CDR3 loop sequences with dual-charged PSA.     

Effects of carrageenan on immune responses. Studies on the macrophage dependency of various antigens after treatment with carrageenan.

Carrageenan, a sulfated polygalactose having macrophage toxic properties, elicited a marked suppression of IgM response to T cell-dependent antigens such as sheep red blood cells (SRBC), dinitrophenylated bovine serum gamma-globulin (DNP-BGG), and trinitrophenylated concanavalin A (TNP-Con A). In contrast, carrageenan did not inhibit antibody responses to such T cell-independent antigens as trinitrophenylated DEAE-dextran (TNP-DEAE-dextran), trinitrophenylated polyvinyl pyrrolidone(TNP-PVP), and trinitrophenylated Ficoll (TNP-Ficoll). Compared to total spleen cells, spleen cells from which macrophages had been removed by adhesion to plastic Petri dishes had less effect on the production of antibody against T cell-dependent antigens, but no change or a rather stimulated effect was observed in in vitro antibiody synthesis against T cell-independent antigens. These results strongly suggest that macrophages are involved in antibody responses to T cell-dependent antigens but not in those to T cell-independent antigens. However, the antibody response to trinitrophenylated lipopolysaccharide (TNP-LPS), a T cell-independent antigen, was inhibited by carrageenan treatment, suggesting that the response is macrophage dependent. Moreover, antibody response to higher doses of dinitrophenylated phytohemagglutinin (DNP-PHA), a T cell-dependent antigen, was shown to be macrophage independent by carrageenan treatment, although the antibody response to low doses of the antigen was macrophage dependent. Considering all these results, carrageenan treatment seems to be a very useful method to determine whether immune response to various antigens are macrophage dependent or not.     

CD4+ T cells mediate abscess formation in intra-abdominal sepsis by an IL-17-dependent mechanism

Abscess formation associated with intra-abdominal sepsis causes severe morbidity and can be fatal. Previous studies have implicated T cells in the pathogenesis of abscess formation, and we have recently shown that CD4(+) T cells activated in vitro by zwitterionic capsular polysaccharides from abscess-inducing bacteria such as Staphylococcus aureus and Bacteroides fragilis initiate this host response when transferred to naive rats. In this study, we show that mice deficient in alphabetaTCR-bearing T cells or CD4(+) T cells fail to develop abscesses following challenge with B. fragilis or abscess-inducing zwitterionic polysaccharides, compared with CD8(-/-) or wild-type animals. Transfer of CD4(+) T cells from wild-type mice to alphabetaTCR(-/-) animals reconstituted this ability. The induction of abscesses required T cell costimulation via the CD28-B7 pathway, and T cell transfer experiments with STAT4(-/-) and STAT6(-/-) mice demonstrated that this host response is dependent on STAT4 signaling. Significantly higher levels of IL-17, a proinflammatory cytokine produced almost exclusively by activated CD4(+) T cells, were associated with abscess formation in Th2-impaired (STAT6(-/-)) mice, while STAT4(-/-) mice had significantly lower levels of this cytokine than control animals. The formation of abscesses was preceded by an increase in the number of activated CD4(+) T cells in the peritoneal cavity 24 h following bacterial challenge. Confocal laser-scanning microscopy analysis revealed that CD4(+) T cells comprise the abscess wall in these animals and produce IL-17 at this site. Administration of a neutralizing Ab specific for IL-17 prevented abscess formation following bacterial challenge in mice. These data delineate the specific T cell response necessary for the development of intra-abdominal abscesses and underscore the role of IL-17 in this disease process.     

Immunosuppressive activity of human seminal plasma. I. Inhibition of in vitro lymphocyte activation.

A high molecular weight fraction prepared from human seminal plasma by gel filtration chromatography suppresses human lymphocyte transformation and DNA synthesis induced by mitogens (PHA, Con A, PWM), antigens (Candida albicans, tetanus toxoid), and allogenic cells. This same fraction also suppresses the stimulated response of mouse lymphocytes to allogenic cells and to various mitogens, including T cell-dependent and T cell-independent mitogens. The induction, but not the expression, of cell-mediated cytotoxicity is also suppressed. Similar high molecular weight fractions suppress the in vitro humoral response of mouse spleen cells to both a T cell-dependent (SRBC) and a T cell-independent (DNP-F) antigen. The high m.w. fraction exhibited in vitro suppressive activity at concentrations of 0.1 to 1.0 mg/ml which corresponds to a 1/50 or greater dilution of human seminal plasma. These observations support the concept that a local immune response against sperm in the female reproductive tract is actively suppressed by a component in seminal plasma.     

An immunomodulatory molecule of symbiotic bacteria directs maturation of the host immune system

The mammalian gastrointestinal tract harbors a complex ecosystem consisting of countless bacteria in homeostasis with the host immune system. Shaped by evolution, this partnership has potential for symbiotic benefit. However, the identities of bacterial molecules mediating symbiosis remain undefined. Here we show that, during colonization of animals with the ubiquitous gut microorganism Bacteroides fragilis, a bacterial polysaccharide (PSA) directs the cellular and physical maturation of the developing immune system. Comparison with germ-free animals reveals that the immunomodulatory activities of PSA during B. fragilis colonization include correcting systemic T cell deficiencies and T(H)1/T(H)2 imbalances and directing lymphoid organogenesis. A PSA mutant of B. fragilis does not restore these immunologic functions. PSA presented by intestinal dendritic cells activates CD4+ T cells and elicits appropriate cytokine production. These findings provide a molecular basis for host-bacterial symbiosis and reveal the archetypal molecule of commensal bacteria that mediates development of the host immune system.     

金针菇子实体多糖分离纯化及结构和免疫活性研究

从金针菇子实体中分离纯化多糖,并对多糖结构和体外免疫活性进行研究。采用水提醇沉法从金针菇子实体中提取粗多糖,利用DEAE-Cellulose-52及Sephacryl S-300HR柱层析纯化得到FVPⅠ-a,再利用HPLC-ELSD技术、红外及核磁共振对FVPⅠ-a进行结构解析。在体外以促RAW264.7巨噬细胞产NO、分泌细胞因子,促进小鼠淋巴细胞增殖实验,考察FVPⅠ-a增强免疫的能力。从金针菇子实体中分离纯化得到FVPⅠ-a,其为分子量81.4kDa,由葡萄糖、果糖和鼠李糖组成的β构型的吡喃型杂多糖。体外免疫实验表明,FVPⅠ-a能够促进RAW264.7巨噬细胞产生NO及分泌细胞因子（IL-1β,IL-6,TNF-α）,能单独的促进小鼠淋巴细胞增殖（P<0.05）,并能协同增强ConA和LPS对小鼠淋巴细胞的促增殖作用（P<0.01,P<0.05）。首次从金针菇子实体中获得FVPⅠ-a杂多糖,其在体外具有增强非特异性免疫反应及增强特异性免疫反应的能力。