J Pappo

University of Texas Medical Branch at Galveston, Galveston, TX, United States

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Publications (29)130.62 Total impact

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    ABSTRACT: In recent years, Abs have been considered a correlate rather than an effector of resistance against Helicobacter pylori infection. However, it is still poorly understood to what extent Ab production correlates with gastric immunopathology. Here we report that Abs not only are dispensable for protection, but they are detrimental to elimination of the bacteria and appear to impair gastric inflammatory responses. We found that the initial colonization with H. pylori bacteria was normal in the B cell-deficient (microMT) mice, whereas at later times (>8 wk) most of the bacteria were cleared, concomitant with the development of severe gastritis. In contrast, wild-type (WT) mice exhibited extensive bacterial colonization and only mild gastric inflammation, even at 16 wk after inoculation. Oral immunizations with H. pylori lysate and cholera toxin adjuvant stimulated comparable levels of protection in microMT and WT mice. The level of protection in both strains correlated well with the severity of the postimmunization gastritis. Thus, T cells were responsible for the gastritis, whereas Abs, including potentially host cell cross-reactive Abs, were not involved in causing the gastritis. The T cells in micro MT and WT mice produced high and comparable levels of IFN-gamma to recall Ag at 2 and after 8 wk, whereas IL-4 was detected after 8 wk only, indicating that Th1 activity dominated the early phase of protection, whereas later a mixed Th1 and Th2 activity was seen.
    The Journal of Immunology 04/2004; 172(8):5024-33. · 5.52 Impact Factor
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    ABSTRACT: The regulatory roles of Th1 and Th2 cells in immune protection against Helicobacter infection are not clearly understood. In this study, we report that a primary H. pylori infection can be established in the absence of IL-12 or IFN-gamma. However, IFN-gamma, but not IL-12, was involved in the development of gastritis because IFN-gamma(-/-) (GKO) mice exhibited significantly less inflammation as compared with IL-12(-/-) or wild-type (WT) mice. Both IL-12(-/-) and GKO mice failed to develop protection following oral immunization with H. pylori lysate and cholera toxin adjuvant. By contrast, Th2-deficient, IL-4(-/-), and WT mice were equally well protected. Mucosal immunization in the presence of coadministered rIL-12 in WT mice increased Ag-specific IFN-gamma-producing T cells by 5-fold and gave an additional 4-fold reduction in colonizing bacteria, confirming a key role of Th1 cells in protection. Importantly, only protected IL-4(-/-) and WT mice demonstrated substantial influx of CD4(+) T cells in the gastric mucosa. The extent of inflammation in challenged IL-12(-/-) and GKO mice was much reduced compared with that in WT mice, indicating that IFN-gamma/Th1 cells also play a major role in postimmunization gastritis. Of note, postimmunization gastritis in IL-4(-/-) mice was significantly milder than WT mice, despite a similar level of protection, indicating that immune protection is not directly linked to the degree of gastric inflammation. Only protected mice had T cells that produced high levels of IFN-gamma to recall Ag, whereas both protected and unprotected mice produced high levels of IL-13. We conclude that IL-12 and Th1 responses are crucial for H. pylori-specific protective immunity.
    The Journal of Immunology 01/2003; 169(12):6977-84. · 5.52 Impact Factor
  • P B Ernst, J Pappo
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    ABSTRACT: Approximately 50% of humanity is infected with Helicobacter pylori. This lifelong infection elicits a marked host response, including a robust gastric IgA response. However, natural infection fails to yield protective immunity. Rather than providing protection, the chronic inflammatory response associated with natural infection can contribute to tissue damage and the pathogenesis of gastroduodenal disease, including atrophic gastritis, peptic ulcer, and gastric cancer. These immune responses are attributed to a subset of helper T cells, so-called Th1 cells, that enhance cell-mediated immunity and induce damage to the gastric epithelium. Thus, it is desirable to have effective vaccines that could prevent and cure infection and that may modify the host response in a manner that prevents immune-mediated disease. Using animal models as a tool to understand the immunobiology of Helicobacter infections, several investigators have shown that effective vaccines can be developed. Thus, prophylactic and even therapeutic vaccines have been described in various animal models. The basis for the effectiveness of these vaccines appears related to their ability to alter the gastric immune response, from a homogeneous Th1 response to a mixed Th1 and Th2 response. Interestingly, immunity can occur in the absence of B cells, suggesting that novel IgA-independent mechanisms exist that confer protection against a luminal infection. Thus, H. pylori infection provides a model with which new mechanisms of immunological protection can be identified and applied to other mucosal infections.
    Acta Odontologica Scandinavica 09/2001; 59(4):216-21. · 1.36 Impact Factor
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    ABSTRACT: The majority of humans infected with Helicobacter pylori maintain a lifelong infection with strains bearing the cag pathogenicity island (PAI). H. pylori inhibits T cell responses and evades immunity so the mechanism by which infection impairs responsiveness was investigated. H. pylori caused apoptotic T cell death, whereas Campylobacter jejuni did not. The induction of apoptosis by H. pylori was blocked by an anti-Fas Ab (ZB4) or a caspase 8 inhibitor. In addition, a T cell line with the Fas rendered nonfunctional by a frame shift mutation was resistant to H. pylori-induced death. H. pylori strains bearing the cag PAI preferentially induced the expression of Fas ligand (FasL) on T cells and T cell death, whereas isogenic mutants lacking these genes did not. Inhibiting protein synthesis blocked FasL expression and apoptosis of T cells. Preventing the cleavage of FasL with a metalloproteinase inhibitor increased H. pylori-mediated killing. Thus, H. pylori induced apoptosis in Fas-bearing T cells through the induction of FasL expression. Moreover, this effect was linked to bacterial products encoded by the cag PAI, suggesting that persistent infection with this strain may be favored through the negative selection of T cells encountering specific H. pylori Ags.
    The Journal of Immunology 08/2001; 167(2):926-34. · 5.52 Impact Factor
  • P B Ernst, J Pappo
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    ABSTRACT: Approximately 50% of humanity is infected with Helicobacter pylori. Normally, this is a life-long infection indicating that the host response to natural infection fails to yield protective immunity. Moreover, the chronic inflammatory response associated with this infection can contribute to tissue damage and the pathogenesis of gastroduodenal disease including atrophic gastritis, peptic ulcer and gastric cancer. These damaging immune responses are attributed to a subset of helper T cells, so-called Th1 cells, that enhance cell-mediated immunity and induce damage to the gastric epithelium. Thus, it is desirable to have effective vaccines that could prevent and cure infection or at least, modify the host response in a manner that prevents immune-mediated disease. Using animal models as a tool to understand the immunobiology of Helicobacter infections, several investigators have shown that effective vaccines can be developed. Thus, prophylactic and even therapeutic vaccines have been described in various animal models. The basis for the effectiveness of these vaccines seems to be found in their ability to alter the gastric immune response, perhaps away from a homogeneous Th1 response towards a mixed Th1 and Th2 response. Using these encouraging approaches, vaccines are being developed for use in humans for the treatment and prevention of H. pylori infection and the gastroduodenal diseases associated with this infection.
    Current Pharmaceutical Design 11/2000; 6(15):1557-73. · 3.31 Impact Factor
  • A Ibraghimov, J Pappo
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    ABSTRACT: Helicobacter pylori infects about half of the world's population. H. pylori elicits marked immune responses, but the infection is commonly life-long. Some infected individuals remain asymptomatic, while others develop significant gastroduodenal disease. We review the underlying host immune response to H. pylori which programs for persistence and evolution of gastroduodenal disease.
    Microbes and Infection 08/2000; 2(9):1073-7. · 2.92 Impact Factor
  • Gastroenterology 01/2000; 118(4). · 12.82 Impact Factor
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    ABSTRACT: The importance of host factors in helicobacter induced gastritis has been shown in animal models. Infection of most mouse strains with Helicobacter felis results in a functional atrophic gastritis, while other strains remain gastritis free. To investigate these host factors further by using genetic crosses of responder and non-responder mice. F(1) hybrids of the non-responder CBA/Ca strain and three strains of mice known to develop H felis induced gastritis were infected for three months with H felis. Gastritis was assessed by histopathology and serum antibody responses by ELISA. Infection of CBA/Ca mice and F(1) hybrids induced little or no gastritis. Analyses of the antibody responses in these mice revealed virtually undetectable anti-helicobacter antibody levels despite colonisation with high numbers of H felis. In contrast, infection of H felis responsive strains induced gastritis and a significant humoral immune response. The non-responsiveness of CBA/Ca mice to H felis infection is dominantly inherited. The lack of gastritis in CBA mice and their offspring is probably due to active suppression of the immune response normally mounted against H felis. Investigation of these mechanisms will provide important insights relevant to induction of gastric atrophy and cancer in humans.
    Gut 10/1999; 45(3):335-40. · 10.73 Impact Factor
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    ABSTRACT: The role of major histocompatibility complex (MHC) class I- and class II-restricted functions in Helicobacter pylori infection and immunity upon oral immunization was examined in vivo. Experimental challenge with H. pylori SS1 resulted in significantly greater (P </= 0.025) colonization of MHC class I and class II mutant mice than C57BL/6 wild-type mice. Oral immunization with H. pylori whole-cell lysates and cholera toxin adjuvant significantly reduced the magnitude of H. pylori infection in C57BL/6 wild-type (P = 0.0083) and MHC class I knockout mice (P = 0.0048), but it had no effect on the H. pylori infection level in MHC class II-deficient mice. Analysis of the anti-H. pylori antibody levels in serum showed a dominant serum immunoglobulin G1 (IgG1) response in immunized C57BL/6 wild-type and MHC class I mutant mice but no detectable serum IgG response in MHC class II knockout mice. Populations of T-cell-receptor (TCR) alphabeta+ CD4(+) CD54(+) cells localized to gastric tissue of immunized C57BL/6 wild-type and MHC class I knockout mice, but TCRalphabeta+ CD8(+) cells predominated in the gastric tissue of immunized MHC class II-deficient mice. These observations show that CD4(+) T cells engaged after mucosal immunization may be important for the generation of a protective anti-H. pylori immune response and that CD4(+) CD8(-) and CD4(-) CD8(+) T cells regulate the extent of H. pylori infection in vivo.
    Infection and Immunity 02/1999; 67(1):337-41. · 4.07 Impact Factor
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    ABSTRACT: Oral immunization with recombinant Helicobacter pylori urease (rUre) coadministered with a mucosal adjuvant protects mice against challenge with Helicobacter felis. In this study, the duration of protection and gastritis after challenge were characterized at sequential time intervals up to 1 year. Outbred Swiss-Webster mice were orally immunized with rUre plus adjuvant and examined for the presence of H. felis infection and leukocyte infiltration into the gastric mucosa. When defined by gastric urease activity, 70%-95% of rUre-immunized mice were protected for between 2 and 57 weeks. Challenge with H. felis increased the inflammatory response in the gastric mucosa of rUre-immunized mice, which also had elevated CD4+ and CD8+ T cells. The CD8+ cells represented a population of gastric intraepithelial cells, which expressed the mucosal alpha E-integrin. Epithelial changes consisting of parietal cell loss and hyperplasia of the epithelium occurred in approximately 20% of the mice. Antimicrobial triple therapy significantly decreased the degree of gastritis and epithelial alteration in the stomach. These results indicate that oral immunization of mice with rUre produces a long-lasting inhibition of H. felis infection but that residual bacteria may produce a persistent lymphocytic infiltration under these experimental conditions.
    Gastroenterology 10/1997; 113(4):1118-28. · 12.82 Impact Factor
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    ABSTRACT: Helicobacter pylori-infected cats were screened by culture and polymerase chain reaction (PCR) for the presence of H. pylori in salivary secretions, gastric juice, gastric tissue and faeces. H. pylori was cultured from salivary secretions in six of 12 (50%) cats and from gastric fluid samples in 11 of 12 (91%) cats. A 298 base pair polymerase chain reactions (PCR) product specific for an H. pylori 26000 MW surface protein was amplified from dental plaque samples from five of 12 (42%) cats and from the faeces of four of five (80%) cats studied. Analyses of serum and mucosal secretions by enzyme-linked immunosorbent assay (ELISA) revealed an H. pylori-specific immunoglobulin G (IgG) response, and elevated IgA anti-H. pylori antibody levels in salivary and local gastric secretions. Immunohistochemical analyses of gastric tissue revealed the presence of IgM+ B cells assembled into multiple lymphoid follicles surrounded by clusters of CD4+ and CD8+ T cells. The lamina propria also contained single cells or aggregates of IgA+ and IgM+ B cells. These observations show that H. pylori can be identified in feline mucosal secretions, and that a localized IgA immune response develops in gastric tissue of H. pylori-infected cats. The findings suggest a zoonotic risk from exposure to personnel handling H. pylori-infected cats in vivaria.
    Immunology 08/1996; 88(3):400-6. · 3.71 Impact Factor
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    ABSTRACT: The ability of oral immunization to interfere with the establishment of infection with Helicobacter felis was examined. Groups of Swiss Webster mice were immunized orally with 250 micrograms of Helicobacter pylori recombinant urease (rUrease) and 10 micrograms of cholera toxin (CT) adjuvant, 1 mg of H. felis sonicate antigens and CT, or phosphate-buffered saline (PBS) and CT. Oral immunization with rUrease resulted in markedly elevated serum immunoglobulin G (IgG), serum IgA, and intestinal IgA antibody responses. Challenge with live H. felis further stimulated the urease-specific intestinal IgA and serum IgG and IgA antibody levels in mice previously immunized with rUrease but activated primarily the serum IgG compartment of PBS-treated and H. felis-immunized mice. Intestinal IgA and serum IgG and IgA anti-urease antibody responses were highest in rUrease-immunized mice at the termination of the experiment. Mice immunized with rUrease were significantly protected (P < or = 0.0476) against infection when challenged with H. felis 2 or 6 weeks post-oral immunization in comparison with PBS-treated mice. Whereas H. felis-infected mice displayed multifocal gastric mucosal lymphoid follicles consisting of CD45R+ B cells surrounded by clusters of Thy1.2+ T cells, gastric tissue from rUrease-immunized mice contained few CD45R+ B cells and infrequent mucosal follicles. These observations show that oral immunization with rUrease confers protection against H. felis infection and suggest that gastric tissue may function as an effector organ of the mucosal immune system which reflects the extent of local antigenic stimulation.
    Infection and Immunity 04/1995; 63(4):1246-52. · 4.07 Impact Factor
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    ABSTRACT: In this study, we demonstrate the role of M cells in uptake of poly(D-L-lactic-co-glycolic acid) (PLGA) microspheres and transport into rabbit Peyer's patches. Microspheres 1 to 10 microns in diameter composed of 50:50 lactic acid:glycolic acid were instilled into intestinal segments containing jejunal or ileal Peyer's patches, and uptake by M cells was examined by electron microscopy. PLGA microspheres visualized as electron-lucent, spherical particles were taken up by M cells by pseudopod-like extensions of the M cell apical membrane and translocated to the pocket region containing mononuclear leukocytes within 60 min. These results indicate that PLGA microspheres can be directed to M cell apical surfaces for delivery to immunocompetent cells in gut-associated lymphoid tissues.
    Cell and Tissue Research 03/1995; 279(2):433-6. · 3.68 Impact Factor
  • Z Kabok, T H Ermak, J Pappo
    Advances in experimental medicine and biology 02/1995; 371A:235-8. · 1.83 Impact Factor
  • T H Ermak, H R Bhagat, J Pappo
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    ABSTRACT: Uptake and delivery of antigens to immunocompetent cells in the gut are critical factors for the development of oral vaccines. Particulate antigens are transported within minutes by M cells to intraepithelial lymphocytes and into the follicle dome. The dome contains B cells, CD4+ T cells, and macrophages, indicating that the cells involved in antigen presentation are located below the dome's epithelium. The high number of M cells in rabbits and the development of monoclonal antibodies against rabbit lymphocytes have enabled the detailed study of lymphocytes associated with M cells. The follicle epithelium of rabbit Peyer's patches contains B cells and a population of CD4-/CD8-, major histocompatibility complex class II+ mononuclear cells of unknown function. These cells are phenotypically distinct from T cells in follicle domes, in T cell-dependent areas, in villus epithelium, or in villus lamina propria. In addition, lymphocytes in M-cell pockets express an activation antigen (3B6) not found on CD4+ or CD8+ cells in T cell-dependent areas. These results indicate that M-cell pocket lymphocytes in follicle epithelium form a phenotypically distinct compartment situated at the interface between M-cell-driven antigen uptake and the mucosal immune system.
    The American journal of tropical medicine and hygiene 02/1994; 50(5 Suppl):14-28. · 2.53 Impact Factor
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    ABSTRACT: Helicobacter felis inoculated per os into germfree mice and their conventional non-germfree counterparts caused a persistent chronic gastritis of approximately 1 year in duration. Mononuclear leukocytes were the predominant inflammatory cell throughout the study, although polymorphonuclear cell infiltrates were detected as well. Immunohistochemical analyses of gastric mucosa from H. felis-infected mice revealed the presence of mucosal B220+ cells coalescing into lymphoid follicles surrounded by aggregates of Thy-1.2+ T cells; CD4+, CD5+, and alpha beta T cells predominated in organized gastric mucosal and submucosal lymphoid tissue, and CD11b+ cells occurred frequently in the mucosa. Follicular B cells comprised immunoglobulin M+ (IgM+) and IgA+ cells. Numerous IgA-producing B cells were present in the gastric glands, the lamina propria, and gastric epithelium. Infected animals developed anti-H. felis serum IgM antibody responses up to 8 weeks postinfection and significant levels of IgG anti-H. felis antibody in serum, which remained elevated throughout the 50-week course of the study.
    Infection and Immunity 07/1993; 61(6):2309-15. · 4.07 Impact Factor
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    J Pappo, R T Mahlman
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    ABSTRACT: The production of interleukin-1 (IL-1) by rabbit Peyer's patch M cells populating the follicle-associated epithelium (FAE) was studied. Sorted 5D9+ phagocytic epithelial M cells synthesized IL-1 after stimulation with lipopolysaccharide (LPS) in vitro, as evidenced by the ability of culture supernatants to induce the proliferation of the T-cell line D10.G4.1. Fixed LPS-stimulated M cells were less effective at mediating T-cell proliferation than supernatants from LPS-activated M cells. The magnitude of T-cell proliferation was M-cell concentration dependent, and proportional to the dose of LPS. The M-cell-mediated D10.G4.1 cell proliferation was inhibited > 75% with anti-IL-1 alpha, but < 50% with similar concentrations of anti-IL-1 beta. The results show that M cells secrete IL-1, and suggest the participation of M cells in the delivery of a localized co-stimulatory signal for T-cell and B-cell proliferation in the microenvironment of gut-associated lymphoid tissue (GALT).
    Immunology 03/1993; 78(3):505-7. · 3.71 Impact Factor
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    J Pappo, T H Ermak, H J Steger
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    ABSTRACT: The ability to deliver particulates to Peyer's patch M cells for uptake into gut-associated lymphoid tissue was examined by administering simultaneously fluorescent green and red polystyrene microspheres into NZW rabbit intestinal loops containing Peyer's patches. Whereas green and red microspheres were taken up by M cells at equivalent concentrations (120 +/- 17 versus 125 +/- 18/mm length of dome), particles conjugated to the anti-M-cell monoclonal antibody 5B11 (IgM, kappa) were internalized by M cells 3-3.5 times more efficiently than conjugates displaying IgM of unrelated specificity (TEPC 183) or native particles of the reciprocal colour inoculated into the same loop at a comparable load. The microspheres formed a concentration gradient from lumen to subepithelial dome, and localized on M-cell apical membranes, M-cell pockets, and subepithelial domes. The transport rate across M cells of 5B11 or TEPC 183 conjugates was similar to that of untreated microspheres. These observations show that intestinal uptake into Peyer's patches can be upregulated by targeting M-cell luminal membrane structures.
    Immunology 08/1991; 73(3):277-80. · 3.71 Impact Factor
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    T H Ermak, H J Steger, J Pappo
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    ABSTRACT: Follicle epithelium and domes of gut-associated lymphoid tissue (GALT) contain populations of lymphocytes which first contact antigen taken up from the intestine. In order to study the association of lymphocytes with M cells in follicle epithelium, monoclonal antibodies (mAb) were generated by immunizing BALB/c mice with lymphocytes populating GALT domes from NZW rabbits, and their specificity was assessed by immunohistochemistry and flow cytometry. mAb 3C10 (IgM) and 3B6 (IgG3) recognized subpopulations of intraepithelial lymphocytes associated with M cells. mAb 3C10 also identified macrophage-lymphocyte clusters in domes and tangible body macrophages in germinal centres of GALT but did not react with cells in T-dependent areas (TDA) or B cells in follicles. mAb 3B6 recognized lymphocytes in domes and B cells in follicles but not T cells in TDA of GALT. The distribution of 3B6+ cells overlapped with, but was more restricted than, that of Ia+ cells. Analysis of lymphocytes in follicle epithelium showed that greater than 95% of lymphocytes associated with M cells were Ia+. T cells represented approximately 95% of intraepithelial lymphocytes in the appendix and approximately 65% in Peyer's patches. A majority of intraepithelial lymphocytes was recognized by mAb 3B6, but mAb 3C10 identified only approximately 30%. Because neither 3C10 nor 3B6 recognized lymphocytes in TDA of GALT, these results indicate that most lymphocytes associated with M cells are a distinct phenotype of Ia+ T cells.
    Immunology 01/1991; 71(4):530-7. · 3.71 Impact Factor
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    M F Heyworth, J Pappo
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    ABSTRACT: The principal aims of this work were (i) to identify the molecular weight (MW) of Giardia muris trophozoite antigens that are recognized by IgA in small intestinal secretions from G. muris-infected mice, and (ii) to determine whether mouse intestinal Giardia-specific IgA is directed against trophozoite surfaces. BALB/c mice were infected with G. muris cysts, and intestinal secretions were harvested from these mice at various times after the start of Giardia infection, and from uninfected mice. Flow cytometry showed that intestinal IgA from G. muris-infected mice, but not from uninfected mice, became bound to trophozoite surfaces in vitro. Western blotting of trophozoite proteins with mouse intestinal secretions showed that IgA from Giardia-infected mice reacted specifically with a broad protein band of approximately 30,000 MW. This finding suggests that one or more trophozoite proteins of approximately 30,000 MW are targets for intestinal antibody in mice infected with G. muris.
    Immunology 09/1990; 70(4):535-9. · 3.71 Impact Factor

Publication Stats

984 Citations
130.62 Total Impact Points

Institutions

  • 2000–2001
    • University of Texas Medical Branch at Galveston
      • Department of Pediatrics
      Galveston, TX, United States
  • 1993–1996
    • Massachusetts Institute of Technology
      • Division of Comparative Medicine
      Cambridge, MA, United States
  • 1990–1993
    • San Francisco VA Medical Center
      San Francisco, California, United States
  • 1988–1989
    • University of California, San Francisco
      • Division of Hospital Medicine
      San Francisco, CA, United States