Ki-Hyang Kim

Calcineurin Inhibitors Block MHC-Restricted Antigen Presentation In Vivo

APCs, like T cells, are affected by calcineurin inhibitors. In this study, we show that calcineurin inhibitors efficiently block MHC-restricted exogenous Ag presentation in vivo. Mice were injected with clinical doses of tacrolimus (FK-506) followed by soluble OVA, and dendritic cells (DCs) were isolated from lymph nodes and spleens. The efficacy of OVA peptide presentation by DCs was evaluated using OVA-specific CD8 and CD4 T cells. Tacrolimus inhibited both class I- and class II-restricted DC presentation of OVA to T cells. Tacrolimus also inhibited both class I- and class II-restricted presentation of OVA in peritoneal macrophages isolated from mice injected with tacrolimus followed by soluble OVA. Tacrolimus-treated peritoneal macrophages, however, were able to present synthetic OVA peptide, SIINFEKL. Inclusion of cyclosporine A to biodegradable microspheres containing OVA greatly reduced their capacity to induce OVA-specific CTL response in mice. These findings provide novel insight into the mode of action of calcineurin inhibitors and have important implications for clinical immunosuppression regimens.

Induction of Potent Antigen-specific Cytotoxic T Cell Response by PLGA-nanoparticles Containing Antigen and TLR Agonist

Previously we showed that biodegradable nanoparticles containing poly-IC or CpG oligodeoxynucleotide (ODN) together with ovalbumin (OVA) were efficient at inducing MHC-restricted presentation of OVA peptides in dendritic cells. The CTL-inducing activities of the nanoparticles were examined in the present study. Nanoparticles containing poly-IC or CpG ODN together with OVA were prepared using biodegradable polymer poly(D,L-lactic acid-co-glycolic acid), and then were opsonized with mouse IgG. The nanoparticles were injected into the tail vein of mice, and 7 days later the OVA-specific CTL activities were measured using an in vivo CTL assay. Immunization of mice with the nanoparticles containing poly-IC or CpG ODN together with OVA elicited potent OVA-specific CTL activity compared to those containing OVA only. In accordance with these results, nanoparticles containing poly-IC or CpG ODN together with OVA exerted potent antitumor activity in mice that were subcutaneously implanted with EG7.OVA tumor cells. These results show that encapsulation of poly-IC or CpG ODN together with antigen in biodegradable nanoparticles is an effective approach for the induction of potent antigen-specific CTL responses in vivo.

Restoration of Electric Footshock-Induced Immunosuppression in Mice by Gynostemma pentaphyllum Components

The immunomodulatory effects of the ethanol extract of Gynostemma pentaphyllum (GP-EX) were examined in electric footshock (EFS)-stressed mice. The mice were orally administered various doses of GP-EX for 7 days before exposure to EFS (duration: 3 min, interval: 10 s, intensity: 2 mA) once a day from day 8 for 14 days with continuous daily feeding of GP-EX. Oral administration of GP-EX to mice prevented EFS stress-induced immunosuppression as determined by the lymphoid organ (thymus and spleen) weight and cellularity. In addition, oral administration of GP-EX restored EFS-suppressed functional properties of mature lymphocytes in terms of concanavalin A-induced proliferation of splenocytes and lipopolysaccharide-induced cytokine production (TNF-α, IL-1β). Furthermore, we found that mice that were orally administered with GP-EX generated much more potent ovalbumin-specific cytotoxic T lymphocyte responses upon intravenous ovalbumin injection compared to the untreated controls. These results demonstrate that oral administration of the ethanol extract of Gynostemma pentaphyllum could increase host defense in immunocompromised situations such as stress-induced immunosuppression.

Processed Aloe vera Gel Ameliorates Cyclophosphamide-Induced Immunotoxicity

The effects of processed Aloe vera gel (PAG) on cyclophosphamide (CP)-induced immunotoxicity were examined in mice. Intraperitoneal injection of CP significantly reduced the total number of lymphocytes and erythrocytes in the blood. Oral administration of PAG quickly restored CP-induced lymphopenia and erythropenia in a dose-dependent manner. The reversal of CP-induced hematotoxicity by PAG was mediated by the functional preservation of Peyer’s patch cells. Peyer’s patch cells isolated from CP-treated mice, which were administered PAG, produced higher levels of T helper 1 cytokines and colony-stimulating factors (CSF) in response to concanavalin A stimulation as compared with those isolated from CP-treated control mice. PAG-derived polysaccharides directly activated Peyer’s patch cells isolated from normal mice to produce cytokines including interleukin (IL)-6, IL-12, interferon-γ, granulocyte-CSF, and granulocyte-macrophage-CSF. The cytokines produced by polysaccharide-stimulated Peyer’s patch cells had potent proliferation-inducing activity on mouse bone marrow cells. In addition, oral administration of PAG restored IgA secretion in the intestine after CP treatment. These results indicated that PAG could be an effective immunomodulator and that it could prevent CP-induced immunotoxic side effects.

Baccatin III, a synthetic precursor of taxol, enhances MHC-restricted antigen presentation in dendritic cells.

Baccatin III, a precursor for the semisynthesis of taxol, is widely considered to be an inactive derivative of taxol. Here we show that baccatin III efficiently enhances MHC-restricted antigen presentation in dendritic cells. Baccatin III increased both class I- and class II-restricted presentation of exogenous OVA in bone marrow-derived dendritic cells (BM-DCs). Baccatin III also increased class I-restricted presentation of virus-encoded endogenous OVA in BM-DCs. Baccatin III did not affect the phagocytic activity of BM-DCs. The antigen presentation-enhancing activity of baccatin III was examined further with nanoparticles containing OVA and baccatin III. Inclusion of baccatin III to nanoparticles containing OVA greatly enhanced their capacity to induce class I-restricted OVA peptide presentation in DCs both in vitro and in vivo. Accordingly, nanoparticles containing both OVA and baccatin III were much more efficient in inducing an OVA-specific CTL response in mice compared to those containing OVA only. These results demonstrate that baccatin III exerts immunomodulatory activities in vivo as well as in vitro on the MHC-restricted antigen presentation.

Identification of HLA‐DR4‐restricted immunogenic peptide derived from xenogenic porcine major histocompatibility complex class I molecule

Park C‐S, Kim K‐H, Im S‐A, Song S, Lee C‐K. Identification of HLA‐DR4‐restricted immunogenic peptide derived from xenogenic porcine major histocompatibility complex class I molecule. Xenotransplantation 2012; 19: 317–322.

Immunomodulatory Effects of Hypocrellin A on MHC-restricted Antigen Processing

Hypocrellin A has gained much attention in recent years due to its light-induced antitumor, antifungal and antiviral activities. Here we report that hypocrellin A exerts immunomodulatory effects on MHC-restricted presentation of antigen. Hypocrellin A inhibited class II-MHC restricted presentation of exogenous antigen, but not class I MHC-restricted presentation of exogenous antigen, in dendritic cells. Hypocrellin A also inhibited the cytosolic pathway of endogenous antigen presentation. However, hypocrellin A did not inhibit the expression of class I and class II MHC molecules on dendritic cells (DCs), the phagocytic activity of DCs, or the H-2Kb-restricted presentation of a synthetic peptide, SIINFEKL. These results show that hypocrellin A differentially modulates the MHC-restricted antigen presentation pathways.

Nanoliposomes of L-lysine-conjugated poly(aspartic acid) Increase the Generation and Function of Bone Marrow- derived Dendritic Cells

Background Biodegradable polymers have increasingly been recognized for various biological applications in recent years. Here we examined the immunostimulatory activities of the novel poly(aspartic acid) conjugated with L-lysine (PLA). Methods PLA was synthesized by conjugating L-lysine to aspartic acid polymer. PLA-nanoliposomes (PLA-NLs) were prepared from PLA using a microfluidizer. The immunostimulatory activities of PLA-NLs were examined in mouse bone marrow-derived dendritic cells (BM-DCs). Results PLA-NLs increased the number of BM-DCs when added to cultures of GM-CSF-induced DC generation on day 4 after the initiation of cultures. Examination of the phenotypic properties showed that BM-DCs generated in the presence of PLA-NLs are more mature in terms of the expression of MHC class II molecules and major co-stimulatory molecules than BM-DCs generated in the absence of PLA-NLs. In addition, the BM-DCs exhibited enhanced capability to produce cytokines, such as IL-6, IL-12, TNF-α and IL-1β. Allogeneic mixed lymphocyte reactions also confirmed that the BMDCs were more stimulatory on allogeneic T cells. PLA- NL also induced further growth of immature BM-DCs that were harvested on day 8. Conclusion These results show that PLA-NLs induce the generation and functional activities of BM-DCs, and suggest that PLA-NLs could be immunostimulating agents that target DCs.

Thapsigargin Increases IL-2 Production in T Cells at Nanomolar Concentrations

Thapsigargin (TGN) is a potent and selective inhibitor of sarco-endoplasmic Ca2+-ATPase, leading to rapid elevation of cytoplasmic Ca2+ concentration. Previous reports have shown that TGN increases the production of various cytokines from macrophages and dendritic cells. Here, we examine the effects of TGN on murine T cells. Nanomolar concentrations of TGN are a significant inducer of IL-2 production with full activity at 50 nM. Micromolar concentrations of TGN, however, are inhibitory to IL-2 production and T cell proliferation. The IL-2 production-inducing activity of TGN is much more prominent when T cells are primed with concanavalin A or anti-CD3 mAb, and is due to the increase of cytoplasmic Ca2+ concentration. TGN at 50 nM does not affect interferon-gamma or IL-4 production from T cells. Thus, the present study shows that low nanomolar concentrations of TGN could be useful in potentiating IL-2 production from antigen-primed T cells.