Polysaccharides derived from Yamoa (Funtumia elastica) prime gammadelta T cells in vitro and enhance innate immune responses in vivo.

Yamoa (ground bark of Funtumia elastica tree) is marketed and sold as a dietary supplement with anecdotal therapeutic effects in the treatment of asthma and hay fever. We determined that Yamoa and Yamoa-derived polysaccharides affected innate immunity, in part, by priming gammadelta T cells. Gene expression patterns in purified bovine gammadelta T cells and monocytes induced by Yamoa were similar to those induced by ultrapure lipopolysaccharide (uLPS). In the presence of accessory cells, Yamoa had priming effects that were similar to those of LPS on bovine and murine gammadelta T cells, but much more potent than LPS on human gammadelta T cells. The bioactive component of Yamoa was delineated to a complex polysaccharide fraction (Yam-I). Intraperitoneal injection of Yamoa and Yam-I in mice induced rapid increases in peritoneal neutrophils directed by changes in chemokine expression. In support of a unique agonist found in Yam-I, similar peritonitis responses were also observed in TLR4- and MyD88-deficient mice. Therapeutic treatment with Yam-I resulted in decreased bacterial counts in feces from mice with Salmonella enterica serotype typhimurium (ST)-induced enterocolitis. This characterization of the immune stimulatory properties of polysaccharides derived from Yamoa suggests mechanisms for the anecdotal positive effects of its ingestion and that these polysaccharides show potential for application in innate protection from disease.

Colutellin A, an immunosuppressive peptide from Colletotrichum dematium.

Colletotrichum dematium is an endophytic fungus recovered from a Pteromischum sp. growing in a tropical forest in Costa Rica. This fungus makes a novel peptide antimycotic, colutellin A, with a MIC of 3.6 microg ml(-1) (48 h) against Botrytis cinerea and Sclerotinia sclerotiorum. Collutellin A has a mass of 1127.7 Da and contains residues of Ile, Val, Ser, N-methyl-Val and beta-aminoisobutryic acid in nominal molar ratios of 3 : 2 : 1 : 1 : 1, respectively. Independent lines of evidence suggest that the peptide is cyclic and sequences of Val-Ile-Ser-Ile and Ile-Pro-Val have been deduced by MS/MS as well as Edman degradation methods. Colutellin A inhibited CD4(+) T-cell activation of interleukin 2 (IL-2) production with an IC(50) of 167.3+/-0.38 nM, whereas cyclosporin A in the same test yielded a value of 61.8 nM. Inhibition of IL-2 production by collutellin A at such a low concentration indicates the potential immunosuppressive activity of this compound. In repeated experiments, cyclosporin A at or above 8 microg ml(-1) exhibited high levels of cytotoxicity on human peripheral blood mononuclear cells, whereas collutellin A or DMSO (carrier) alone, after 24 and 48 h of culture, exhibited no toxicity. Because of these properties collutellin A has potential as a novel immunosuppressive drug.

Antigen-independent priming: a transitional response of bovine gammadelta T-cells to infection.

Analysis of global gene expression in immune cells has provided unique insights into immune system function and response to infection. Recently, we applied microarray and serial analysis of gene expression (SAGE) techniques to the study of gammadelta T-cell function in humans and cattle. The intent of this review is to summarize the knowledge gained since our original comprehensive studies of bovine gammadelta T-cell subsets. More recently, we have characterized the effects of mucosal infection or treatment with microbial products or mitogens on gene expression patterns in sorted gammadelta and alphabeta T-cells. These studies provided new insights into the function of bovine gammadelta T-cells and led to a model in which response to pathogen-associated molecular patterns (PAMPs) induces 'priming' of gammadelta T-cells, resulting in more robust responses to downstream cytokine and/or antigen signals. PAMP primed gammadelta T-cells are defined by up-regulation of a select number of cytokines, including MIP1alpha and MIP1beta, and by antigens such as surface IL2 receptor alpha (IL-2Ralpha) and CD69, in the absence of a prototypic marker for an activated gammadelta T-cell, IFN-gamma. Furthermore, PAMP primed gammadelta T-cells are more capable of proliferation in response to IL-2 or IL-15 in the absence of antigen. PAMPs such as endotoxin, peptidoglycan and beta-glucan are effective gammadelta T-cell priming agents, but the most potent antigen-independent priming agonists defined to date are condensed oligomeric tannins produced by some plants.

Response of gammadelta T Cells to plant-derived tannins.

Many pharmaceutical drugs arc isolated from plants used in traditional medicines, and new plant-derived pharmaceutical drugs continue to be identified. Relevant to this review, different plant-derived agonists for gammadelta T cells are described that impart effector functions upon distinct subsets of these cells. Recently, plant tannins have been defined as one class of gammadelta T cell agonist and appear to preferentially activate the mucosal population. Mucosal gammadelta T cells function to modulate tissue immune responses and induce epithelium repair. Select tannins, isolated from apple peel, rapidly induce immune gene transcription in gammadelta T cells, leading to cytokinc production and increased responsiveness to secondary signals. Activity of these tannin preparations tracks to the procyanidin fraction, with the procyanidin trimer (C1) having the most robust activity defined to date. The response to the procyanidins is evolutionarily conserved in that responses are seen with human, bovine, and murine gammadelta T cells, although human cells show less selectivity. Procyanidin-induced responses described in this review likely account for the expansion of mucosal gammadelta T cells seen in mice and rats fed soluble extracts of tannins. Use of procyanidins to activate gammadelta T cells may represent a novel approach for the treatment of tissue damage and autoimmune diseases.

Differential regulation of CD11b on gammadelta T cells and monocytes in response to unripe apple polyphenols.

Leukocyte adhesion and migration are mediated partially by CD11b/CD18 (membrane-activated complex-1, CR3). Earlier studies have demonstrated a role for green tea polyphenols in down-regulating CD11b on CD8(+) T cells and monocytes. We have shown recently a stimulatory effect of unripe apple polyphenols (APP) on gammadelta T cells. Thus, we compared the effect of APP on bovine gammadelta T cell and monocyte CD11b expression. Purified bovine monocytes and monocyte-depleted PBLs were cultured with APP. CD11b levels decreased on monocytes in response to APP. In contrast, a gammadelta T cell subset responded to APP by up-regulating CD11b. The CD11b regulation was not seen on gammadelta T cells or monocytes treated with APP fractions depleted of tannins. The APP-induced down-regulation of CD11b on monocytes was inhibited by an anti-CD11b mAb, consistent with previous studies showing that polyphenols bind CD11b. As expected, the anti-CD11b mAb had no effect on the APP response in resting gammadelta T cells, as these cells lacked CD11b. Consistent with the changes in surface CD11b expression, APP-treated gammadelta T cells showed increased adherence to plastic, whereas monocyte adhesion was reduced. APP also induced cytokine gene expression in gammadelta T cells. Some polyphenols are thought of as anti-inflammatory agents; however, these data, as well as other ongoing studies, indicate they have a proinflammatory effect on gammadelta T cells. In vivo, plant polyphenols may enhance gammadelta T cell migration and function at sites of inflammation, where they could induce rapid, immune-regulatory and innate-like immune responses.

A comprehensive SAGE database for the analysis of gammadelta T cells.

Gammadelta T cells have been conserved since the adaptive immune system arose, yet their importance is still unclear. In an attempt to compensate for the lack of a broad knowledge base of gammadelta T cells across species, global analyses of gammadelta T cell transcriptomes have been performed using serial analysis of gene expression (SAGE). Twelve new SAGE libraries were generated from the following bovine lymphocyte populations: magnetic bead-sorted blood gammadelta T cells, spleen gammadelta T cells and enriched spleen alphabeta T cells from a single calf, both rested and Con A/IL2 stimulated, and flow cytometry-sorted blood gammadelta and alphabeta T cells each either rested, Con A/IL2, or phorbol 12 myristate 13-acetate/ionomycin stimulated. These new libraries complement two earlier SAGE libraries of circulating gammadelta T cell subsets. These databases were analyzed using new web-based bioinformatic tools, which allow the user to rapidly compare gene expression patterns within these and other SAGE and standard expressed sequence tag libraries generated from different cell types and different species. These analyses revealed striking differences between blood and spleen gammadelta T cells and how these cells respond to mitogenic stimulation. These analyses also confirm previous studies that suggested that global gene expression in gammadelta and alphabeta T cells is quite similar; however, a 5-fold increase in gammadelta T cell-specific transcripts could be induced by Con A/IL2 stimulation. These new public databases provide additional resources for the annotation/analysis of global gene expression in gammadelta T cells, which will facilitate studies of the biology of this enigmatic lymphoid cell.