Tim O'Sullivan

Tim O'Sullivan*

615 Charles E. Young Drive South
Los Angeles, CA 90095


Assistant Professor, Microbiology, Immunology & Molecular Genetics
Member, Basic/Translational Research, Jonsson Comprehensive Cancer Center, Cell & Developmental Biology GPB Home Area, Eli & Edythe Broad Center of Regenerative Medicine & Stem Cell Research, Immunity, Microbes & Molecular Pathogenesis GPB Home Area
Research Interests

Our research is dedicated to understanding the molecular mechanisms responsible for protective or pathologic immune responses during cancer, viral infection, and obesity. We will exploit this knowledge to design effective therapeutic strategies with potential clinical applications for type II diabetes and cancer. Our research program is composed of three major directions:

1. Mechanisms of immune surveillance and immune escape in cancer

Our research goal is to dissect the cellular and molecular mechanisms that control tissue-resident and circulating innate immunosurveillance and tumor escape. Our previous work demonstrated that the innate immune system could protect mice from tumor development (O’Sullivan et al., J Exp Med 2012).  

We are interested in the following questions:

-How are tissue-resident immune cells activated by developing cancer?

-How are circulating Natural Killer (NK) cells recruited into the tumor microenvironment?

-What are the molecular and cellular mechanisms that lead to NK cell dysfunction in the tumor microenvironment? 

2. Mechanisms of adipose tissue inflammation and insulin resistance during diet-induced obesity

Our research was the first to identify protective and pathologic roles for tissue-resident type 1 innate lymphoid cells (ILC1) during viral infection, liver injury, and obesity (O’Sullivan et al., Immunity 2016; Weizman et al., Cell 2017; Nabekura et al., Immunity 2019). 

We are interested in the following questions: 

-What is the complete cellular composition of mammalian adipose tissue?

-How do cells interact in the adipose tissue micronevironment during homeostasis and obesity?

-What causes adipose tissue inflammation during obesity?

3. ILC responses to viral infection and generation of immunological memory

The innate immune system was previously considered to be composed of short-lived cells that perform effector functions during infection and then rapidly die once their task is accomplished. However, our studies and others suggest that ILCs posses characteristics of the adaptive immune system, such as clonal expansion, longevity, and immunological memory (O’Sullivan et al., Immunity 2015; Weizman et al., Nature Immunology 2019)

We are interested in the following questions: 

-What are the transcriptional and epigenetic mechanisms that control memory cell formation?

-How do effector lymphocytes survive to form memory cells?



Dr. O’Sullivan is an Assistant Professor of Microbiology, Immunology, and Molecular Genetics. He received his Bachelors of Science Degree (B.S.) from Cornell University and his Doctor of Philosophy Degree (Ph.D.) in Biomedical Science from the University of California San Diego. Dr. O’Sullivan’s thesis work focused on the interactions between the innate immune system and cancer. Dr. O’Sullivan subsequently completed his American Cancer Society postdoctoral fellowship at Memorial Sloan Kettering Cancer Center where he studied the role of circulating and tissue-resident innate lymphoid cells (ILC) during viral infection and diet-induced obesity. Dr. O’Sullivan established his own laboratory at UCLA in 2017.


A selected list of publications: