Bio

Professional Education


  • Bachelor of Science, Kyung Hee University (2003)
  • Master of Science, Catholic University of Korea (2006)
  • Doctor of Philosophy, Pohang Inst Science & Technology (2014)

Stanford Advisors


Publications

All Publications


  • Clinical and immunomodulatory effects of transcutaneous vagal nerve stimulation for idiopathic gastroparesis Gottfried-Blackmore, A., Namkoong, H., Adler, E. P., Fernandez-Becker, N., Clarke, J., Habtezion, A., Nguyen, L. WILEY. 2020
  • Distinct immune characteristics distinguish hereditary and idiopathic chronic pancreatitis. The Journal of clinical investigation Lee, B., Adamska, J. Z., Namkoong, H., Bellin, M. D., Wilhelm, J. J., Szot, G. L., Louis, D. M., Davis, M. M., Pandol, S., Habtezion, A. 2020

    Abstract

    Chronic pancreatitis (CP) is considered an irreversible fibroinflammatory pancreatic disease. Despite numerous animal model studies, questions remain about local immune characteristics in human CP. We profiled pancreatic immune cell characteristics in control organ donors and CP patients that included hereditary and idiopathic CP undergoing total pancreatectomy with islet auto-transplantation. Flow cytometric analysis revealed a significant increase in the frequency of CD68+ macrophages in idiopathic CP. In contrast, hereditary CP showed a significant increase in CD3+ T cell frequency, which prompted us to investigate the T cell receptor beta (TCRbeta) repertoire in CP and controls. TCRbeta-sequencing revealed a significant increase in TCRbeta repertoire diversity and reduced clonality in both CP groups versus controls. Interestingly, we observed differences in Vbeta-Jbeta gene family usage between hereditary and idiopathic CP and a positive correlation of TCRbeta rearrangements with disease severity scores. Immunophenotyping analyses in hereditary and idiopathic CP pancreata indicate differences in innate and adaptive immune responses, which highlights differences in immunopathogenic mechanism of disease among subtypes of CP. TCR repertoire analysis further suggests a role for specific T cell responses in hereditary versus idiopathic CP pathogenesis providing new insights into immune responses associated with human CP.

    View details for DOI 10.1172/JCI134066

    View details for PubMedID 32053120

  • Dysbiosis-Induced Secondary Bile Acid Deficiency Promotes Intestinal Inflammation. Cell host & microbe Sinha, S. R., Haileselassie, Y., Nguyen, L. P., Tropini, C., Wang, M., Becker, L. S., Sim, D., Jarr, K., Spear, E. T., Singh, G., Namkoong, H., Bittinger, K., Fischbach, M. A., Sonnenburg, J. L., Habtezion, A. 2020

    Abstract

    Secondary bile acids (SBAs) are derived from primary bile acids (PBAs) in a process reliant on biosynthetic capabilities possessed by few microbes. To evaluate the role of BAs in intestinal inflammation, we performed metabolomic, microbiome, metagenomic, and transcriptomic profiling of stool from ileal pouches (surgically created resevoirs) in colectomy-treated patients with ulcerative colitis (UC) versus controls (familial adenomatous polyposis [FAP]). We show that relative to FAP, UC pouches have reduced levels of lithocholic acid and deoxycholic acid (normally the most abundant gut SBAs), genes required to convert PBAs to SBAs, and Ruminococcaceae (one of few taxa known to include SBA-producing bacteria). In three murine colitis models, SBA supplementation reduces intestinal inflammation. This anti-inflammatory effect is in part dependent on the TGR5 bile acid receptor. These data suggest that dysbiosis induces SBA deficiency in inflammatory-prone UC patients, which promotes a pro-inflammatory state within the intestine that may be treated by SBA restoration.

    View details for DOI 10.1016/j.chom.2020.01.021

    View details for PubMedID 32101703

  • Pyruvate controls the checkpoint inhibitor PD-L1 and suppresses T cell immunity. The Journal of clinical investigation Watanabe, R., Shirai, T., Namkoong, H., Zhang, H., Berry, G. J., Wallis, B. B., Schaefgen, B., Harrison, D. G., Tremmel, J. A., Giacomini, J. C., Goronzy, J. J., Weyand, C. M. 2017; 127 (7): 2725–38

    Abstract

    Patients with coronary artery disease (CAD) are at high risk for reactivation of the varicella zoster virus (VZV) and development of herpes zoster (HZ). Here, we found that macrophages from patients with CAD actively suppress T cell activation and expansion, leading to defective VZV-specific T cell immunity. Monocyte-derived and plaque-infiltrating macrophages from patients with CAD spontaneously expressed high surface density of the immunoinhibitory ligand programmed death ligand-1 (PD-L1), thereby providing negative signals to programmed death-1+ (PD-1+) T cells. We determined that aberrant PD-L1 expression in patient-derived macrophages was metabolically controlled. Oversupply of the glycolytic intermediate pyruvate in mitochondria from CAD macrophages promoted expression of PD-L1 via induction of the bone morphogenetic protein 4/phosphorylated SMAD1/5/IFN regulatory factor 1 (BMP4/p-SMAD1/5/IRF1) signaling pathway. Thus, CAD macrophages respond to nutrient excess by activating the immunoinhibitory PD-1/PD-L1 checkpoint, leading to impaired T cell immunity. This finding indicates that metabolite-based immunotherapy may be a potential strategy for restoring adaptive immunity in CAD.

    View details for PubMedID 28604383

  • Diversification of the antigen-specific T cell receptor repertoire after varicella zoster vaccination. Science translational medicine Qi, Q., Cavanagh, M. M., Le Saux, S., Namkoong, H., Kim, C., Turgano, E., Liu, Y., Wang, C., Mackey, S., Swan, G. E., Dekker, C. L., Olshen, R. A., Boyd, S. D., Weyand, C. M., Tian, L., Goronzy, J. J. 2016; 8 (332): 332ra46-?

    Abstract

    Diversity and size of the antigen-specific T cell receptor (TCR) repertoire are two critical determinants for successful control of chronic infection. Varicella zoster virus (VZV) that establishes latency during childhood can escape control mechanisms, in particular with increasing age. We examined the TCR diversity of VZV-reactive CD4 T cells in individuals older than 50 years by studying three identical twin pairs and three unrelated individuals before and after vaccination with live attenuated VZV. Although all individuals had a small number of dominant T cell clones, the breadth of the VZV-specific repertoire differed markedly. A genetic influence was seen for the sharing of individual TCR sequences from antigen-reactive cells but not for repertoire richness or the selection of dominant clones. VZV vaccination favored the expansion of infrequent VZV antigen-reactive TCRs, including those from naïve T cells with lesser boosting of dominant T cell clones. Thus, vaccination does not reinforce the in vivo selection that occurred during chronic infection but leads to a diversification of the VZV-reactive T cell repertoire. However, a single-booster immunization seems insufficient to establish new clonal dominance. Our results suggest that repertoire analysis of antigen-specific TCRs can be an important readout to assess whether a vaccination was able to generate memory cells in clonal sizes that are necessary for immune protection.

    View details for DOI 10.1126/scitranslmed.aaf1725

    View details for PubMedID 27030598

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