Andrew Ramstead

Oenothein B, a cyclic dimeric ellagitannin isolated from Epilobium angustifolium, enhances IFNγ production by lymphocytes.

Oenothein B is a polyphenol isolated from Epilobium angustifolium and other plant sources, which has been reported to exhibit immunomodulatory properties. Oenothein B is known to activate myeloid cells and induce the production of IL-1 and other cytokines. However, its effects on lymphocytes are unknown. In this report, we show that oenothein B stimulated innate lymphocytes, including bovine and human γδ T cells and NK cells, resulting in either increased CD25 and/or CD69 expression. We also demonstrate that oenothein B enhanced the production of interferon-γ (IFNγ) by bovine and human NK cells alone and in combination with interleukin-18 (IL-18), a response not observed with other commonly studied polyphenols. Furthermore, we demonstrate that oenothein B enhanced the production of IFNγ by human T cells. Since IFNγ contributes to antitumor, antibacterial, and antiviral cell responses, these data suggest an additional mechanism that could account, at least in part, for the immune enhancing properties of oenothein B.

Comparative biology of γδ T cell function in humans, mice, and domestic animals.

γδ T cells are a functionally heterogeneous population and contribute to many early immune responses. The majority of their activity is described in humans and mice, but the immune systems of all jawed vertebrates include the γδ T cell lineage. Although some aspects of γδ T cells vary between species, critical roles in early immune responses are often conserved. Common features of γδ T cells include innate receptor expression, antigen presentation, cytotoxicity, and cytokine production. Herein we compare studies describing these conserved γδ T cell functions and other, potentially unique, functions. γδ T cells are well documented for their potential immunotherapeutic properties; however, these proposed therapies are often focused on human diseases and the mouse models thereof. This review consolidates some of these studies with those in other animals to provide a consensus for the current understanding of γδ T cell function across species.

Tolerogen-induced interferon-producing killer dendritic cells (IKDCs) protect against EAE

Natural killer (NK) cells and dendritic cells (DCs) have been shown to link the innate and adaptive immune systems. Likewise, a new innate cell subset, interferon-producing killer DCs (IKDCs), shares phenotypic and functional characteristics with both DCs and NK cells. Here, we show IKDCs play an essential role in the resolution of experimental autoimmune encephalomyelitis (EAE) upon treatment with the tolerizing agent, myelin oligodendrocyte glycoprotein (MOG), genetically fused to reovirus protein σ1 (termed MOG-pσ1). Activated IKDCs were recruited subsequent MOG-pσ1 treatment of EAE, and disease resolution was abated upon NK1.1 cell depletion. These IKDCs were able to kill activated CD4(+) T cells and mature dendritic DCs, thus, contributing to EAE remission. In addition, IKDCs were responsible for MOG-pσ1-mediated MOG-specific regulatory T cell recruitment to the CNS. The IKDCs induced by MOG-pσ1 expressed elevated levels of HVEM for interactions with cognate ligand-positive cells: LIGHT(+) NK and T(eff) cells and BTLA(+) B cells. Further characterization revealed these activated IKDCs being MHC class II(high), and upon their adoptive transfer (CD11c(+)NK1.1(+)MHC class II(high)), IKDCs, but not CD11c(+)NK1.1(+)MHC class II(intermediate/low) (unactivated) cells, conferred protection against EAE. These activated IKDCs showed enhanced CD107a, PD-L1, and granzyme B expression and could present OVA, unlike unactivated IKDCs. Thus, these results demonstrate the interventional potency induced HVEM(+) IKDCs to resolve autoimmune disease.

Aging influences the response of T cells to stimulation by the ellagitannin, oenothein B.

Several plant extracts, including certain polyphenols, prime innate lymphocytes and enhance responses to secondary stimuli. Oenothein B, a polyphenol isolated from Epilobium angustifolium and other plant sources, enhances IFNγ production by both bovine and human NK cells and T cells, alone and in response to secondary stimulation by cytokines or tumor cells. Innate immune cell responsiveness is known to be affected by aging, but whether polyphenol responses by these cells are also impacted by aging is not known. Therefore, we examined oenothein B responsiveness in T cells from cord blood, young, and adult donors. We found that oenothein B stimulates bovine and human T cells from individuals over a broad range of ages, as measured by increased IL-2Rα and CD69 expression. However, clear differences in induction of cytokine production by T cells were seen. In T cells from human cord blood and bovine calves, oenothein B was unable to induce IFNγ production. However, oenothein B induced IFNγ production by T cells from adult humans and cattle. In addition, oenothein B induced GM-CSF production by human adult T cells, but not cord blood T cells. Within the responsive T cell population, we found that CD45RO+ memory T cells expressed more cytokines in response to oenothein B than CD45RO- T cells. In summary, our data suggest that the immunostimulation of T cells by oenothein B is influenced by age, particularly with respect to immune cytokine production.

Complex role of γδ T-cell-derived cytokines and growth factors in cancer.

γδ T cells are innate lymphocytes that recognize and kill a range of tumor cells and are currently being explored as a target for tumor immunotherapy. However, γδ T cells play a complex role in cancer and can promote, as well as inhibit, tumor growth. In addition to tumor cell killing, γδ T cells express a number of cytokines and other soluble factors in response to tumors. Soluble factors expressed by γδ T cells in these settings include interferon-γ, tumor necrosis factor-α, interleukin (IL)-4, IL-10, transforming growth factor-β, IL-17, and a number of growth factors. These factors have differing and sometimes opposing effects on antitumor immunity and tumor angiogenesis, and likely contribute to the complex role of these cells in cancer. Here, we review studies in both mice and humans that examine differential cytokine secretion by γδ T cells in response to tumors and tumor immunotherapy, and discuss the influence of these γδ T-cell-derived factors on tumor growth.

Therapeutic Potential of Polyphenols from Epilobium Angustifolium (Fireweed)

Epilobium angustifolium is a medicinal plant used around the world in traditional medicine for the treatment of many disorders and ailments. Experimental studies have demonstrated that Epilobium extracts possess a broad range of pharmacological and therapeutic effects, including antioxidant, anti‐proliferative, anti‐inflammatory, antibacterial, and anti‐aging properties. Flavonoids and ellagitannins, such as oenothein B, are among the compounds considered to be the primary biologically active components in Epilobium extracts. In this review, we focus on the biological properties and the potential clinical usefulness of oenothein B, flavonoids, and other polyphenols derived from E. angustifolium. Understanding the biochemical properties and therapeutic effects of polyphenols present in E. angustifolium extracts will benefit further development of therapeutic treatments from this plant. Copyright

Amphotericin B stimulates γδ T and NK cells, and enhances protection from Salmonella infection:

Amphotericin B (AmB) is a commonly used antifungal drug, with well-documented effects on cellular immune responses. We determined that AmB-stimulated γδ T-cell activation and proliferation in vitro at very low concentrations. AmB also enhanced IFN-γ production by NK cells in combination with IL-18. AmB had a greater effect on IFN-γ production in cells isolated from very young animals. Although innate immunostimulatory aspects of AmB have been defined, AmB has not been extensively applied in non-fungal infection settings. Given that γδ T cells are increased and activated in Salmonella infection in cattle, we assessed the effects of AmB in protection from Salmonella enterocolitis in calves. One injection of AmB, at approximately one-tenth of the concentration used in human patients to counter fungal infection, or saline control, was delivered intravenously to calves prior to infection with Salmonella. This single injection caused no adverse effects, reduced disease symptoms from Salmonella enterocolitis and significantly reduced Salmonella bacteria shed in feces of infected animals. Our findings suggest that AmB may be an inexpensive and readily available prophylactic approach for the prevention of bacterial infection in calves.

Roles of Toll-Like Receptor 2 (TLR2), TLR4, and MyD88 during Pulmonary Coxiella burnetii Infection

ABSTRACT Coxiella burnetii, the causative agent of Q fever, is an obligate intracellular, primarily pulmonary, bacterial pathogen. Although much is known about adaptive immune responses against this bacterium, our understanding of innate immune responses against C. burnetii is not well defined, particularly within the target tissue for infection, the lung. Previous studies examined the roles of the innate immune system receptors Toll-like receptor 2 (TLR2) and TLR4 in peripheral infection models and described minimal phenotypes in specific gene deletion animals compared to those of their wild-type controls (S. Meghari et al., Ann N Y Acad Sci 1063:161–166, 2005, http://dx.doi.org/10.1196/annals.1355.025; A. Honstettre et al., J Immunol 172:3695–3703, 2004, http://dx.doi.org/10.4049/jimmunol.172.6.3695) . Here, we assessed the roles for TLR2, TLR4, and MyD88 in pulmonary C. burnetii infection and compared responses to those that occurred in TLR2- and TLR4-deficient animals following peripheral infection. As observed previously, neither TLR2 nor TLR4 was needed for limiting bacterial growth after peripheral infection. In contrast, TLR2 and, to a lesser extent, TLR4 limited growth (or dissemination) of the bacterium in the lung and spleen after pulmonary infection. TLR2, TLR4, and MyD88 were not required for the general inflammatory response in the lungs after pulmonary infection. However, MyD88 signaling was important for infection-induced morbidity. Finally, TLR2 expression on hematopoietic cells was most important for limiting bacterial growth in the lung. These results expand on our knowledge of the roles for TLR2 and TLR4 in C. burnetii infection and suggest various roles for these receptors that are dictated by the site of infection.

Type I Interferon Counters or Promotes Coxiella burnetii Replication Dependent on Tissue

ABSTRACT Coxiella burnetii is an intracellular pathogen and the cause of Q fever. Gamma interferon (IFN-γ) is critical for host protection from infection, but a role for type I IFN in C. burnetii infection has not been determined. Type I IFN supports host protection from a related pathogen, Legionella pneumophila, and we hypothesized that it would be similarly protective in C. burnetii infection. In contrast to our prediction, IFN-α receptor-deficient (IFNAR−/−) mice were protected from C. burnetii-induced infection. Therefore, the role of type I IFN in C. burnetii infection was distinct from that in L. pneumophila. Mice treated with a double-stranded-RNA mimetic were protected from C. burnetii-induced weight loss through an IFNAR-independent pathway. We next treated mice with recombinant IFN-α (rIFN-α). When rIFN-α was injected by the intraperitoneal route during infection, disease-induced weight loss was exacerbated. Mice that received rIFN-α by this route had dampened interleukin 1β (IL-1β) expression in bronchoalveolar lavage fluids. However, when rIFN-α was delivered to the lung, bacterial replication was decreased in all tissues. Thus, the presence of type I IFN in the lung protected from infection, but when delivered to the periphery, type I IFN enhanced disease, potentially by dampening inflammatory cytokines. To better characterize the capacity for type I IFN induction by C. burnetii, we assessed expression of IFN-β transcripts by human macrophages following stimulation with lipopolysaccharide (LPS) from C. burnetii. Understanding innate responses in C. burnetii infection will support the discovery of novel therapies that may be alternative or complementary to the current antibiotic treatment.