Principal Investigators

Sheri Krams, PhD

Associate Professor
Department of Surgery
Program in Immunology


Ph.D., University of California, Davis
Postdoctoral Fellowship, University of California, San Francisco

Research Interests:
Functions of microRNAs in transplantation
Identification and function of NK cells
Apoptosis and tissue damage in transplantation and liver disease

We have begun studies directed at elucidating the roles of microRNAs in transplantation. After profiling global miRNA expression in human small bowel biopsy, we discovered that unsupervised hierarchical clustering of microRNA patterns could distinguished rejecting from non-rejecting biopsies. Liver transplant outcome is also significantly affected by viral recurrence or reactivation in the post-transplant period, in part exacerbated by the immunosuppressed status of the host immune system. We have developed a model using rat orthotopic liver transplantation and total lymphoid irradiation (TLI) to study the immune mechanisms of tolerance induction in liver allograft recipients. Our studies suggest that concomitant viral infection can augment alloimmune responses in liver allograft recipients and can perturb the immune regulatory mechanisms that promote tolerance. Our studies have challenged the paradigm that NK cells do not participate in the rejection of solid organ grafts. We have demonstrated that recipient-derived NK cells not only infiltrate rejecting liver grafts early after transplantation but also are a significant source of IFNg thus bridging the innate and adaptive immune responses post transplant. We examined the activation receptors involved in the interaction of NK cells with dendritic cells (DC) since NK cells have the potential to mediate both maturation and killing of DC and this could alter T cell priming post-tarnsplant. Using RNAi techniques we demonstrated that DC stimulation of NK cells to produce IFNg is mediated through NKp46 and that NK cell killing of DC is independent of NKp30, NKp46 and NKG2D. Our studies indicate that NK cells interact with DC and tumors through distinct activating receptors – NKp46 and NKp30/NKG2D respectively. These data are important for the development of therapeutics that will target NK-DC interactions post-transplant without compromising the ability of NK cells to kill virally-infected or transformed cells.

Olivia Martinez

Department of Surgery
Program in Immunology


Ph.D., University of California, Berkeley

Research Interests:
Cytokine regulation of alloreactivity
Growth and survival of EBV+ B cell lymphomas
Cytokine signal transduction pathways
Immune mechanisms of tolerance post-transplantation

I have two major areas of focus in the laboratory. First, I am interested in Epstein Barr Virus-mediated mechanisms of immune evasion with particular focus on resistance to cell death receptor pathways of apoptosis in EBV B cell lymphomas, the characterization of the human T cell response to EBV infected B cells, host microRNAs induced by EBV infection and effects of immunosuppressive drugs on growth and survival of EBV B cell lymphomas. The second area of study addresses tolerance induction in solid organ transplantation. Specifically, examining the generation and characterization of regulatory T cells in allogeneic responses and the role of alternate co-stimulatory molecules in alloreactivity.

Carlos O. Esquivel, MD, PhD

Professor of Surgery
Chief, Division of Transplantation
Director, Liver Transplant Program


M.D., University of Costa Rica
Ph.D., University of Lund, Sweden

Research Interests:

The molecular mechanisms of rejection
Induction of tolerance to achieve full acceptance of transplanted organs

Lab Manager and Clinical Research Coordinator

Mary Gay Lapasaran, MD

Life Science Research Professional 2
Clinical Research Coordinator
Lab Manager


MD, University of Santo Tomas, Philippines
B.S. Public Health, University of the Philippinesy

Research Interests:

I handle the clinical studies mainly involving immune mechanisms of certain viruses in transplant recipients in children and adults. To be able to interact with patients and their family and to be able to contribute to a better understanding to cure or treat certain diseases has always been why research has been of importance to me.

Post-Doctoral Fellows

Yarl Balachandran, MD

Surgical Resident
Postdoctoral Scholar in Transplantation Surgery


MD, Harvard Medical School
BA, Columbia University

Research Interests:

Post-Transplant Lymphoproliferative Disorder (PTLD) is the most common malignancy in children who have undergone solid organ transplantation and are on chronic immunosuppression. The lack of proven biomarkers to reliably identify PTLD or those patients at highest risk has hindered advances in the field. Given this, my research is focused on investigating possible biomarkers for PTLD. In particular, I assess gain-of-function mutations in the Epstein-Barr virus (EBV) protein LMP1 and identify microRNAs associated with EBV-positive PTLD. I also assist with the ongoing NIH-funded Clinical Trials in Organ Transplantation in Children (CTOT-C) study. I was recently invited to present at the NIH and American Transplant Congress.

Marla McPherson

Marla McPherson, PhD

Postdoctoral Researcher


Ph.D. (Genetics and Genomics), University of California Davis, 2016
B.S. (Biological Sciences), University of Connecticut, 2010

Research Interests:

As a postdoctoral fellow, my research will focus on Epstein Barr Virus (EBV)-based modulation of the host human gene expression network within infected B cells. The goal is to investigate mechanisms of EBV-induced cellular proliferation and oncogenic transformation (cancer). An aspiration for the research is that an improved understanding of the mechanisms in EBV pathogenesis will help identify new therapeutic targets in EBV+ post-transplant lymphoproliferative disorders and, ultimately, improve outcomes for EBV+ organ transplant patients who develop this disorder.

Marc Lucia Perez, PhD



PhD in Biomedicine, University of Barcelona
Biotechnology Graduate, Autonomous University of Barcelona

Research Interests:

I am interested in studying the TCR and BCR repertories and its possible use as a Biomarker for immunological related events in the context of Solid Organ transplantation.

Graduate Students

James Harden

PhD Student, Immunology


B.S., Davidson College

Research Interests:

I use a murine cardiac allograft transplant model to study mechanisms of immune suppression that facilitates allograft prolongation and prevents rejection. My current focus is on the immunosuppressive contribution of hepatic plasmacytoid dendritic cells (pDC) and the role of miR-181 in pDC function.

Eden Maloney

PhD Candidate, Immunology


B.S., University of California, Los Angeles

Research Interests:

Research Description: I'm using deep-sequencing to create a genomic atlas of EBV to reveal how EBV genomic diversity varies in health and disease, specifically how EBV contributes to oncogenesis. Additionally, I am using bioinformatics to understand how EBV contributes to cancer in various tissue types.

Jiaying Toh

PhD Student, Immunology


BSc Biomedical Sciences, University College
London, United Kingdom

Research Interests:

Research Description: Interactions between EBV+ PTLD and the immune system.

Medical and Summer Students

Vincent Busque

Undergraduate Student, Stanford University

Sin Ting (Abbie) Hui

Stanford Institutes of Medicine Summer Research Program
Undergraduate Student, Brown University

Claudia Moreno Romero

Stanford Summer Research Program
Undergraduate Student, St. Mary's University - San Antonia, Texas

Sharjeel Syed

Medical Student, Stanford University School of Medicine
Bachelor's Degree, Biology Concentrated in Biochemistry, Middle Eastern Studies