Mitogenic Lectins Research Articles

The Glycan Ectodomain of SARS-CoV-2 Spike Protein Modulates Cytokine Production and Expression of CD206 Mannose Receptor in PBMC Cultures of Pre-COVID-19 Healthy Subjects.

The ability of recombinant, SARS-CoV-2 Spike (S) protein to modulate the production of two COVID-19 relevant, pro-inflammatory cytokines (IL-6 and IFN-γ) in PBMC cultures of healthy, pre-COVID-19 subjects was investigated. We observed that cytokine production was largely and diversely modulated by the S protein depending on antigen or mitogen stimulation, as well as on the protein source, insect (S-in) or human (S-hu) cells. While both proteins co-stimulated cytokine production by polyclonally CD3-activated T cells, PBMC activation by the mitogenic lectin Concanavalin A (Con A) was up-modulated by S-hu protein and down-modulated by S-in protein. These modulatory effects were likely mediated by the S glycans, as demonstrated by direct Con A-S binding experiments and use of yeast mannan as Con A binder. While being ineffective in modulating memory antigenic T cell responses, the S proteins and mannan were able to induce IL-6 production in unstimulated PBMC cultures and upregulate the expression of the mannose receptor (CD206), a marker of anti-inflammatory M2 macrophage. Our data point to a relevant role of N-glycans, particularly N-mannosidic chains, decorating the S protein in the immunomodulatory effects here reported. These novel biological activities of the S glycan ectodomain may add to the comprehension of COVID-19 pathology and immunity to SARS-CoV-2.

Assessment of the role of anthocyanin standardized elderberry (Sambucus nigra) extract as an immune-stimulating nutraceutical of Nile tilapia, Oreochromis niloticus.

The study of nutraceuticals and their connection to immunity is an expanding field of research. The use of nutraceuticals to alleviate stress and enhance immunity in adverse aquaculture environments have been examined to a certain extent. To elucidate the understanding, we focused on the immunological effect of membrane-separated 13% anthocyanin standardized elderberry (EB) extract with maltodextrin excipient, widely used first-line nutraceuticals to augment the immunity, in aquaculture fish, Nile tilapia. To evaluate the potential of EB-extract, we assessed their capability to enhance lymphocyte proliferation and interleukin-2 production in an in-vitro condition using spleen and thymus lymphocytes. The experiments on spleen and thymus T-cells demonstrated significantly higher T-cell proliferation by EB-extract when lectin mitogen Con A was present as a stimulator. Likewise, our spleen B-cell proliferation result reveals a significant effect of EB-extracts, along with B-cell stimulator non-lectin mitogen LPS. Further, the quantification of IL-2 indicates elevated IL-2 levels when spleen T-cells were cultured with EB-extracts and with Con A present as a stimulator. These suggest that 13% anthocyanin standardized EB-extracts can aggrandize fish cells' cellular and humoral immune responses. With further research, elderberry extracts could be used to supplement commercial feed in aquaculture to reduce stress and stimulate the immune response.

Insect galectin stimulates the human CD4+ T cell proliferation by regulating inflammation (T cell and monocyte) through Th2 immune response

In this study, the galectin (OrGal) was purified from the grub of rhinoceros beetle (Oryctes rhinoceros) (Coleoptera: Scarabaeidae) using lactose-affinity chromatography and its molecular mass was determined as 191 kDa. The OrGal binds lactose, galactose and BSM. It is a heterotrimer whose IEF were ∼5–5.5 (50 kDa), 7 (75 kDa) and 8 (95 kDa). The OrGal was glycine-rich and showed peptide-homology to galectin and mitogenic lectin. From the isolated human PBMC, CD4+ T and CD19+ B cells were sorted and confirmed with CD markers. The OrGal was mitogenic to T-cells but not B cells (24 h and 48 h), and this activity was repressed by lactose. Expression of inflammatory mediators showed that OrGal upregulated IL-2 and IL-4, and downregulated IFN-γ, IL-6 and GM-CSF in LPS-primed-T-cells. In the LPS-primed-monocytes, OrGal downregulated NF-κB, TNF-α, IL-1β, IL-6, IL-12 and NO. The de novo transcriptomics identified transcripts (PB 3585.1 & PB 3817.1) showing identity to Coleopteran galectin-4, − 6, − 8 and − 9, in which galectin-8 & − 4 showed high similarities. Mass spectrometry sequences of OrGal and its subunit exhibited a considerable identity to PB 3585.1 (galectin-8) & PB 3817.1 (galectin-4). The in silico models of above two transcripts interacted with lactose and galactose.

Effect of different fatty acids on the proliferation and cytokine production of dairy cow peripheral blood mononuclear cells

During the transition period, dairy cows often experience negative energy balance, which induces metabolic and immunological disturbances. Our previous work has shown a relationship between the inhibition of immune functions and increased blood nonesterified fatty acid (NEFA) levels. In this study, we evaluated the effect of 11 fatty acids (palmitoleic, myristic, palmitic, stearic, oleic, linoleic, docosahexaenoic, conjugated linoleic, lauric, eicosapentaenoic, and linolenic acids) as well as a mix that represented the NEFA profile observed during the transition period at different concentrations (0, 50, 100, and 250 µM) on proliferation and cytokines secretion of lymphocytes. To assess lymphoproliferation, peripheral blood mononuclear cell (PBMC) from 5 healthy cows (166-189 d in milk) were isolated, stimulated with the mitogenic lectin concanavalin A (ConA), incubated for 72 h with or without fatty acids, and subjected to flow cytometry analysis. Our results showed that all fatty acids, except lauric acid, significantly reduced proliferation of PBMC in a dose-dependent manner. The most detrimental effect was observed with conjugated linoleic and stearic acids, where proliferation of PBMC was already inhibited at the lowest dose (50 µM). For cytokine secretion, we found that levels of IL-4 in culture supernatant of ConA-stimulated PBMC were reduced after a 24-h exposure to the lowest dose (50 µM) of oleic and palmitoleic acids. A dose of 100 µM of eicosapentaenoic acid, NEFA mixture, and myristic acid was necessary to observe a reduction in IL-4 levels. The PBMC also showed a decrease in the secretion of IFN-γ in response to lauric, linolenic, palmitoleic, and stearic acids at 50 µM and myristic acid at 100 µM. Overall, polyunsaturated fatty acids were more potent inhibitors of cytokine secretions than saturated fatty acids. In addition, we detected an inverse relationship between the melting points of fatty acids and their ability to inhibit IL-4 and IFN-γ secretions, as evidenced by greater inhibition with low-melting point fatty acids. Overall, our study confirmed that NEFA have a negative effect on some lymphocyte functions, and that their inhibitory effect on cytokine secretions increases with the degree of unsaturation.

Purification and characterisation of a xylose-specific mitogenic lectin from Fusarium sambucinum

A xylose-specific intracellular lectin, showing hemagglutination only with rabbit erythrocytes was purified from mycelium of Fusarium sambucinum which was designated as FSL. An array of anion exchange chromatography on Q-Sepharose and gel-exclusion chromatography on Sephadex G-100 resulted in 84.21% yield and 53.99-fold purification of lectin with specific activity of 169.53 titre/mg. Molecular weight of FSL determined by SDS-PAGE was 70.7 kDa, which was further confirmed by gel-exclusion chromatography. Native-PAGE analysis of FSL showed its monomeric nature. FSL was observed to be a glycoprotein containing 2.9% carbohydrate. Hapten inhibition profile of FSL displayed its strong affinity towards D-xylose (MIC 1.562 mM), L-fucose (MIC 6.25 mM), D-mannose (MIC 3.125 mM), fetuin (MIC 15.62 μg/mL), asialofetuin (MIC 125 μg/mL) and BSM (MIC 3.125 μg/mL). Affinity of FSL towards xylose is rare. FSL was found stable over a pH range 6.0–7.5 and upto 40 °C temperature. Hemagglutination activity of FSL remained unaffected by divalent ions. Lectin concentration of 5 μg/mL was found sufficient to stimulate proliferation of murine spleen cells and its concentration 75 μg/mL exhibited highest mitogenic potential. FSL exhibited maximum mitogenic stimulatory index of 14.35. The purification, characterisation and mitogenicity of F. sambucinum lectin has been reported first time.

Purification of a potent mitogenic homodimeric Penicillium griseoroseum lectin and its characterisation.

Penicillium griseoroseum lectin was 80-fold purified by successive DEAE Sepharose anion exchange and Sephadex G-100 gel permeation chromatography. P. griseoroseum lectin exhibited haemagglutination activity towards protease-treated rabbit erythrocytes. It showed specificity towards various carbohydrates such as d-mannose, N-acetyl-d-glucosamine, mucins, and so forth. P. griseoroseum lectin was found as a glycoprotein with glycan content of 4.33%. Purified P. griseoroseum lectin is homodimeric having a molecular mass of 57 kDa with subunit molecular mass of 28.6 kDa. Haemagglutination activity of purified P. griseoroseum lectin was completely stable from 25°C to 35°C at a pH range of 6-7.5. Lectin activity was not influenced by divalent metal ions and denaturants. P. griseoroseum lectin manifested mitogenicity towards mice splenocytes and activity reached a peak at 75 μg/ml of lectin concentration. P. griseoroseum lectin in microgram concentrations stimulated proliferation of mice splenocytes. Thus, P. griseoroseum lectin exhibits potential mitogenicity, which can be exploited for further biomedical applications.

Purification and characterization of a mitogenic lectin from Penicillium duclauxii

Lectins are proteins/glycoproteins of non-immune origin which interact specifically and non-covalently with carbohydrate moieties on the cell surface. In this study, a lectin was purified from Penicillium duclauxii by ion-exchange chromatography on DEAE-Sepharose and gel filtration chromatography on a Sephadex G-100 column. An overall recovery of 94.11% and 60-fold purification was achieved. The purified lectin had a molecular weight of 54.9 kDa and was found to be heterogeneous as revealed by double band of sub-units with molecular mass of 21.13 kDa and 33.26 kDa, under reducing conditions. It is a glycoprotein with carbohydrate content of 3.95%. Lectin induced haemagglutination of erythrocytes was inhibited strongly by glycoproteins such as bovine submaxillary mucin, porcine stomach mucin and fetuin. The maximum haemagglutinating activity of P. duclauxii lectin was maintained after incubation at a temperature and pH range of 20–35 °C and 6.0–8.0, respectively. The haemagglutinating activity of P. duclauxii lectin was unaffected by EDTA and various metal ions. The purified P. duclauxii lectin exhibited maximum mitogenic activity towards mouse splenocytes at a concentration of 75 μg/mL. This manuscript reports a novel lectin from P. duclauxii with potent mitogenic activity towards mouse splenocytes.

A mitogenic lectin from Rhizoctonia bataticola arrests growth, inhibits metastasis, and induces apoptosis in human colon epithelial cancer cells.

The correlation between colorectal cancer (CRC) progression and altered expression of N-glycans can be considered in search for new biomarkers and anticancer agents to control CRC. Earlier N-glycan specific mitogenic lectin from Rhizoctonia bataticola (RBL) has been reported which has growth inhibitory and apoptotic effect on human ovarian and leukemic cells, but mitogenic effect on normal PBMCs revealing its clinical potential. Here, we report the effect of RBL on human colon cancer HT 29, SW480, and SW620 cell growth and its differential binding to human normal colon and cancer tissues. RBL has strong binding to both primary and metastatic colon cancer cells with MFI of 403, 404, and 192, respectively for HT 29, SW480, and SW620 cells. RBL shows dose and time dependent growth inhibitory effect with IC50 of 5, 6.4, and 6.8 µg/mL, respectively for HT 29, SW480, and SW620 cells. RBL inhibited the clonogenicity of colon carcinoma cells. RBL arrests metastatic SW620 cell growth at S phase, increased hypodiploid population by 6.1%, 14.3%, and 23.2%, respectively at 12, 24, and 36 h. Further, RBL induces SW620 cell apoptosis in time dependent manner, showed increased release of ROS and nuclear degradation compared to lectin untreated control. Adhesion, wound healing, invasion, and migration assays demonstrated anti-metastasis effect of RBL in SW620 cells apart from its growth inhibitory effect. Anti angiogenic effect of RBL was demonstrated by CAM assay. All these results show the promising potential of RBL both as diagnostic and therapeutic agent.

Mitogenic lectins from Cephalosporium curvulum (CSL) and Aspergillus oryzae (AOL) mediate host-pathogen interactions leading to mycotic keratitis.

A core-fucose-specific lectin, CSL from Cephalosporium curvulum, has been reported earlier. Here we assign the role for CSL and another lectin AOL, from pathogenic fungus Aspergillus oryzae, in causing mycotic keratitis. CSL and AOL show strong binding to immortalized and primary human corneal epithelial cells (HCECs) which are inhibited by asialofetuin, confirming their glycan-mediated binding. CSL and AOL showed increase in viability at lower concentrations (0.07µg/ml) whereas at higher concentrations (0.15µg/ml and 0.30µg/ml), have inhibitory effect on immortalized HCECs. Lectin-mediated effect was comparable with the effect induced by the Colony Forming Units (CFUs) of C. curvulum and A. oryzae. CFUs induced more than 1.5-fold increase in HCECs proliferation. Both lectins and fungal CFUs induce secretion of proinflammatory cytokines IL6 and IL8 implicated in ocular diseases. This was supported by upregulation of TLR2 and 4 by lectins as revealed by flow cytometry and RT-PCR. CSL and AOL mediate host-pathogen interactions leading to mycotic keratitis. The mechanism of pathogenesis is possibly initiated through surface binding of mycelia through the lectins to TLR2/4 followed by upregulation of proinflammatory cytokines IL6, IL8 and TLR2 and 4. Understanding the mechanism of pathogenesis is of clinical significance in designing and developing therapeutic strategy to control the infection.

Exquisite specificity of mitogenic lectin from Cephalosporium curvulum to core fucosylated N-glycans.

Lectins are carbohydrate binding proteins that are gaining attention as important tools for the identification of specific glycan markers expressed during different stages of the cancer. We earlier reported the purification of a mitogenic lectin from human pathogenic fungus Cephalosporium curvulum (CSL) that has complex sugar specificity when analysed by hapten inhibition assay. In the present study, we report the fine sugar specificity of CSL as determined by glycan array analysis. The results revealed that CSL has exquisite specificity towards core fucosylated N-glycans. Fucosylated trimannosyl core is the basic structure required for the binding of CSL. The presence of fucose in the side chain further enhances the avidity of CSL towards such glycans. The affinity of CSL is drastically reduced towards the non-core fucosylated glycans, in spite of their side chain fucosylation. CSL showed no binding to the tested O-glycans and monosaccharides. These observations suggest the unique specificity of CSL towards core fucosylated N-glycans, which was further validated by binding of CSL to human colon cancer epithelial and hepatocarcinoma cell lines namely HT29 and HepG2, respectively, that are known to express core fucosylated N-glycans, using AOL and LCA as positive controls. LCA and AOL are fucose specific lectins that are currently being used clinically for the diagnosis of hepatocellular carcinomas. Most of the gastrointestinal markers express core fucosylated N-glycans. The high affinity and exclusive specificity of CSL towards α1-6 linkage of core fucosylated glycans compared to other fucose specific lectins, makes it a promising molecule that needs to be further explored for its application in the diagnosis of gastrointestinal cancer.

CEACAM1 deficiency exacerbates acute liver injury in a mouse model of immune-mediated hepatitis

Introduction: Injection of a sublethal dose of the T cell mitogenic plant lectin concanavalin A (ConA) induces acute immune-mediated liver injury. Hallmarks of liver injury are increased plasma transaminase activities and the release of pro-inflammatory cytokines. CEACAM1 is a cellular adhesion molecule that is expressed on epithelia, endothelia, and leukocytes. Originally, CEACAM1 has been identified as an intercellular homophilic adhesion molecule on hepatocytes. The CEACAM1 isoform with a long cytoplasmic domain contains an immune receptor tyrosine-based inhibition motif (ITIM) that is pivotal in for its negative regulation of leukocyte activation.

Structural analysis and binding properties of isoforms of tarin, the GNA-related lectin from Colocasia esculenta

The lectins, a class of proteins that occur widely in animals, plants, fungi, lichens and microorganisms, are known for their ability to specifically bind to carbohydrates. Plant lectins can be classified into 12 families including the Galanthus nivalis agglutinin (GNA)-related lectin superfamily, which is widespread among monocotyledonous plants and binds specifically to mannose, a behavior that confers remarkable anti-tumor, anti-viral and insecticidal properties on these proteins. The present study characterized a mitogenic lectin from this family, called tarin, which was purified from the crude extract from taro (Colocasia esculenta). The results showed that tarin is a glycoprotein with 2–3% carbohydrate content, composed of least 10 isoforms with pIs ranging from 5.5 to 9.5. The intact protein is a heterotetramer of 47kDa composed of two non-identical and non-covalently associated polypeptides, with small subunits of 11.9kDa and large subunits of 12.6kDa. The tarin structure is stable and recovers or maintains its functional structure following treatments at different temperatures and pH. Tarin showed a complex carbohydrate specificity, binding with high affinity to high-mannose and complex N-glycans. Many of these ligands can be found in viruses, tumor cells and insects, as well as in hematopoietic progenitor cells. Chemical modifications confirmed that both conserved and non-conserved amino acids participate in this interaction. This study determined the structural and ligand binding characteristics of a GNA-related lectin that can be exploited for several different purposes, particularly as a proliferative therapeutic molecule that is able to enhance the immunological response.

Human pleural B-cells regulate IFN-γ production by local T-cells and NK cells in aMycobacterium tuberculosis-induced delayed hypersensitivity reaction

DTH (delayed type hypersensitivity) reactions are secondary cellular immune responses that appear 24-72 h after antigen exposure. Tuberculous pleurisy is a common manifestation of extrapulmonary TB (tuberculosis) and is considered a human model of Th1-mediated DTH. In order to identify functional cross-talk among cellular populations sited in this inflammatory microenvironment, we analysed phenotypic and functional features of human B-cells isolated from the PF (pleural fluid) of TB patients. Freshly isolated PF-B-cells displayed a lower expression of CD20, CD1d and HLA-DR, and a higher expression of CD95, CD38, CD25, CXCR3 (CXC chemokine receptor 3) and CXCR4 (CXC chemokine receptor 4) than their PB (peripheral blood) counterparts, suggesting a non-classical in situ activation. Although memory PF-T-cell frequencies were increased, the frequencies of memory PF-B-cells were not. We demonstrated that, upon stimulation with γ-irradiated M. tuberculosis, mycobacterially secreted proteins or a lectin mitogen, PF-B-cells had a strong activation and produced IL-10 by a mechanism that was dependent on bystander activation of CD19(-) PF cells. Besides, within PF cells, B-cells diminished in vitro M. tuberculosis-induced IFN (interferon)-γ production by T-cells and NK (natural killer) cells in an IL-10-dependent manner. Finally, we found that the lower the frequency of B-cells, the higher the ratio of IFN-γ/IL-10 within PF. Thus our results suggest that B-cells can regulate a human DTH reaction induced by M. tuberculosis.

Revisiting the first long-term culture of antigen-specific cytotoxic T cells.

Revisiting the first long-term culture of antigen-specific cytotoxic T cells.

Lignosulfonic acid exhibits broad-spectrum anti-HIV and anti-HSV activity and has potential for microbicidal applications

Multiple clinical studies show the importance of genital HSV-2 infections in women on the sexual transmission of HIV-1 and vice versa. Therefore, it is important to develop molecules with potent dual antiviral activity to reduce sexual transmission of these life-treating pathogens. Here, we describe that the polyanionic compound lignosulfonic acid (LA; MW: 8000), which belongs to the family of lignin-derived macromolecules, is a cheap byproduct that is formed during the conversion of wood pulp into paper. LA exhibits low toxicity (CC50: >62.5 µM) and potent broad-spectrum anti-HIV activity (IC50s: 0.10 - 0.34 µM), irrespective of the viral coreceptor tropism. In addition, it inhibits the formation of giant cells between HIV-1 persistently infected cells and non-infected CD4 target T cells (IC50: 0.23 µM). HSV-2 is not solely an epitheliotropic virus, as it also infects CD4 T cells, macrophages and MDDCs. We show that LA is able to inhibit HSV-2 infection in HIV-1 susceptible T cells in the lower µM-range (IC50: 0.78-0.82 µM). In addition, LA blocks viral replication of dual HIV-1 and HSV-2 infected cells with comparable potency (IC50: 0.71 µM). DC-SIGN plays an important role in the sexual transmission of HIV and of HSV. We could show that LA (12.5 µM) has no effect on the capture of HIV by Raji.DC-SIGN cells, however it inhibited further transmission to uninfected CD4 T cells (IC50: 1.2 µM). Comparable observations were made with HSV-2 using MDDCs and MT-4 cells (IC50: 1.1 µM). We investigated also its potential side-effects and stimulatory effects. PBMCs were exposed to high amounts of LA and the expression of CD25, CD69 and HLA-DR on CD4+ T cells was measured. No significant increased effects were seen for each activation marker, while the mitogenic lectin PHA stimulated. Finally, LA did not harm the vaginal lactobacilli and synergistic activity was observed with acyclovir, PRO2000 and the lantibiotic LabyA1. In conclusion, lignosulfonic acid has potential for a microbicidal agent.

Effects of Euphorbia milii latex on mitogen-induced lymphocyte proliferation

The crude latex of "Crown-of-Thorns" (Euphorbia milii var hislopii, syn E.splendens) is a potent plant molluscicide. For this reason, toxicological studies have been performed to evaluate the health risks posed by its use in schistosomiasis control programs. The present study is part of a more comprehensive immunotoxicological evaluation of this molluscicide. Here, we investigated the effects of E. milii latex on the proliferation of human lymphocytes in vitro. Lyophilized latex of E. milii (0, 0.5, 5, 25 and 50 µg/ml) was incubated with whole blood in the presence of proliferation stimulators, i.e. lectins (phytohemagglutinin, concanavalin A and pokeweed mitogen), as well as with human monoclonal antibody against CD3 and tetanus toxoid. Cell proliferation was measured by ³H-thymidine incorporation, and the effects of latex on mitogen-induced cell proliferation were compared to the effects of 10 ng/ml of 12-O-tetradecanoylphorbol-13-acetate (TPA). Results showed that mitogen-induced cell proliferation was markedly enhanced by E. milii latex. This synergistic effect of latex on mitogen-induced lymphocyte proliferation may be due to the presence of TPA-like phorbol esters and/or to mitogenic plant lectins.

Rachycentron canadum (cobia) Lectin Promoted Mitogenic Response in Mice BALB/c Splenocytes

The mitogenic lectins are invaluable tools to study the biochemical changes associated with lymphocyte activation and proliferation of various immune cells. Rachycentron canadum lectin (RcaL) was detected and purified from serum of cobia fish. The aim of this study was to evaluate the proliferative response and cytokine production in splenocytes of mice in vitro stimulated with RcaL lectin; Canavalia ensiformis lectin (Con A) was used as positive control. A high proliferation index was induced by RcaL in relation to control cells. Furthermore, RcaL induced higher IL-2 and IL-6 production in relation to control. The cell viability was 90% in splenocytes treated with RcaL lectin, but RcaL promoted significant late apoptosis after 24 and 48 h in relation to control. RcaL induced proliferative responses suggesting that this lectin can be used as a mitogenic agent in immunostimulatory assays.

Tracking the repertoire of human adult and neonatal T cells during ex vivo amplification

[Extract] In times of limited material, expansion of T cells in vitro has become a standard practice across many clinical and basic immunological procedures; such as haematopoietic stem cell transplantation, the study of biopsy specimens, immunomonitoring of clinical trial patients and the study of samples from neonates and children. Classically, mitogenic lectins, such as phytohaemagglutinin (PHA-P) or the phorbol esterphorbol 12-myristate 13-acetate, have been used for initiating T cell expansion. However, a more physiologically relevant method of T cell stimulation mimics the interaction with antigen-presenting cells through the use of anti-CD3 and anti-CD28 monoclonal antibodies (mAb) (Martin et al, 1986). This procedure has been improved in recent years, by fusing anti-CD3 and anti-CD28 mAb to microbead structures (Pene et al, 2003). Here, the initial signal is provided by CD3 molecule activation and the co-stimulatory signal is provided by CD28 molecule activation. In this study, we assessed whether human T-activator CD3/CD28 Dynabeads or PHA-P could amplify T cells from human umbilical cord blood (UCB) or adult peripheral blood mononuclear cells (PBMC) without distorting the baseline ex vivo T cell repertoire.

Neutralization of mitogenic lectins by intravenous immunoglobulin (IVIg) prevents T cell activation: does IVIg really have a direct effect on T cells?

Intravenous immunoglobulin (IVIg) is used for the treatment of an increasing number of autoimmune diseases. Clinical observations on IVIg-treated patients have revealed a modulation of T cell populations and functions in these patients. In vitro studies aimed at understanding the mechanisms underlying the effects of IVIg on T cells led to the conclusion that IVIg directly affected lectin-activated T cell functions. However, more recent studies have suggested the absence of a direct effect of IVIg on T cells. In the present work, we revisited the effect of IVIg on T cells using lectin-stimulated human T cells and showed that IVIg inhibited T cell functions only when added simultaneously with the activating lectin. Further, we showed that IVIg depleted from lectin-reactive IgG was no longer inhibitory, suggesting that the effect of IVIg on T cells was the consequence of lectin neutralization, possibly by interaction with glycans present in F(ab')(2) portion of IgG molecules. Our results challenge the previously widely accepted notion that IVIg exerts its anti-inflammatory effects by acting directly on T cells and suggest that effects of IVIg observed in treated patients are rather a consequence of the recently reported inhibitory effect of IVIg on antigen presentation.

In vitro and in vivo immunomodulatory and anti-ulcerogenic activities of Teucrium ramosissimum extracts

Teucrium ramosissimum (Lamiaceae), a native and endemic plant from South Tunisia, has traditionally been used as a treatment for inflammation and for ulcers. Though the plant and its products are widely used, very few studies have analyzed the pharmacological/toxicological properties of this plant. Thus, the aim of these studies was to evaluate the anti-inflammatory/anti-ulcerogenic activities of various extracts (i.e., methanolic, aqueous, and total oligomer flavonoid [TOF]-enriched) from leaves of T. ramosissimum. In vitro, the effects from each extract on lysosomal enzyme activity and proliferation of, respectively, freshly isolated peritoneal macrophages and splenic lymphocytes were assessed. The extracts alone clearly affected macrophage function, as evidenced by a significant modulation of cell lysosomal enzyme activity and ability to form and/or release nitric oxide. These extracts were also found to be able to significantly modify the proliferation of splenocytes, even when lipopolysaccharide or lectin mitogens were absent. With respect to the anti-ulcerogenic activity of the extracts, these studies found that the leaf extracts were able to exert significant protective effects against ethanol-induced ulcers in a rat model; at some doses, the extract effects were even greater than that obtained using a cytoprotective histamine H2-antagonist, cimetidine. Based on these studies, we conclude that the extracts from T. ramosissimum appear to be potentially potent modulators of innate immunity and that their efficacy against ulcer formation may be due, in part, to a cytoprotective effect. Further, these results fortify the ethnopharmacological importance of the use of T. ramosissimum products as anti-inflammatory and anti-ulcer agents. Nevertheless, ongoing/further studies are needed to clarify more precisely mechanisms underlying effects against ulcers and on lymphocyte and macrophage functionality, as well as the causative agents.