Basic Biology V
Blood stem cells living in the bone marrow of adult humans give rise to all of the cells in our blood, including the red blood cells that carry oxygen to supply our body, and the white blood cells such as T and B lymphocytes that fight infections and keep us healthy. Among the T lymphocytes there is a small population called invariant natural killer T (iNKT) cells. Despite their low frequency in humans (~0.001-1% in blood), iNKT cells have the remarkable capacity to mount immediate and potent responses when stimulated, and have been suggested to play important roles in regulating multiple human diseases including infections, allergies, cancer, and autoimmunity (such as Type I diabetes and multiple sclerosis). However, successful clinical interventions with iNKT cells have been greatly hindered by our limited knowledge on how these cells are produced by blood stem cells, largely due to the lack of tools to track these cells in humans. We therefore propose a novel model system to overcome this research bottleneck by transplanting human blood stem cells into a mouse and genetically programming these cells to develop into iNKT cells. This “humanized” mouse model will allow us to directly track the differentiation of human blood stem cells into iNKT cells in a living animal. From this study, we will address some critical unanswered questions for iNKT cell development, and shed light on developing stem-cell based iNKT cell therapies.
Statement of Benefit to California:
Allergies, cancer and autoimmunity are leading health hazards in California. These diseases affect millions of Californians, impairing their life quality and creating huge economic burdens for the State of California. This proposal intends to study invariant natural killer (iNKT) T cells, a special population of T lymphocytes that have been suggested to play important roles in regulating these diseases. To date, clinical applications of iNKT cells have been greatly limited by their low frequency in humans and their high variability between individuals (~0.001-1% in blood). Thus, an improved understanding of how these cells are naturally generated is important for their use clinically. Like all other cells in blood, iNKT cells are descendants of the blood stem cells that live in the bone marrow of adult humans. Our goal is to study how human blood stem cells give rise to iNKT cells. If successful, our results can be exploited to develop stem cell-based iNKT cell therapies to treat allergies, cancer and autoimmunity, and therefore may benefit the millions of Californians currently suffering from these diseases. In addition, the knowledge and reagents generated from this proposed study will be shared freely with non-profit and academic organizations in California, and any new intellectual property derived from this study will be developed under the guidance of CIRM to benefit the State of California.
Blood stem cells that reside in the bone marrow of adult humans give rise to all of the cells in our blood through differentiation of hematopoietic stem cells (HSCs). This includes the white blood cells such as T and B lymphocytes that fight infections and keep us healthy. There are many types of T lymphocytes that differentiate from HSCs, including some rare forms. Invariant natural killer T (iNKT) cells are one such cell and have been suggested to play important roles in human conditions such as infections, allergies, cancer, and autoimmunity. However, rare human T lymphocyte populations have proven difficult to study in vivo. The goal of this Exploratory Concepts Award proposal is to overcome this hurdle by modifying human HSCs to express specific cell markers such that expression of the marker will result in clonal lines of human iNKT cells and to use this population to generate a humanized mouse model where the differentiation of HSCs into iNKT cells can be studied in vivo following transplantation. The approach will enable investigators to investigate iNKT cell lineage and sublineage differentiation in vivo. If successful, the study will answer key questions in the basic biology of human hematopoietic stem cell differentiation. Novelty and Transformative Potential - The hypothesis is not entirely novel since much of it is based on previous publications and others are working with similar systems. However, the system is not completely understood, and the proposal would likely continue to advance the field. - The proposal is appropriate to the Exploratory Concept Award since, if successful, these studies could produce preliminary data that would support research applicable to a broad immunology field. - If the applicant’s hypothesis of TCR instruction is demonstrated, it would establish a dogma in the field, and if harnessed appropriately, it is possible to even allow for tailored immunotherapies for a variety of diseases. - However, if the instruction model is not supported by the initial studies, little will be gained from the studies, and there is little insight as to how the investigator will determine the mechanism. Feasibility and Experimental Design - The Aims and experimental design will directly address the proposed hypothesis and enable meaningful conclusions to be drawn. - A concern was noted regarding the subtle heterogeneity of immune cells and a research plan offering little insight into the methods that confirm successful differentiation among these closely related groups. - More genes of the receptor in question should be tested since insufficient justification was presented for the selection of just 2 genes. - Overexpression of the receptor in immature T-cell precursors has been shown to disrupt T-cell development and may compromise the experimental system. - Appropriate facilities are available to successfully conduct the proposed research. Principal Investigator (PI) and Research Team - The PI has published a number of papers in high-impact journals and has appropriate experience to perform the experiments. The level of commitment appears appropriate to successfully complete the proposed studies. -The collaborative team is excellent and adds to the likelihood that the proposed project will be successful. Responsiveness to the RFA - The research is related to stem cell biology and is highly responsive to the RFA. The mechanisms of commitment of HSCs into distinct hematopoietic lineages are also responsive to the RFA. Stem cells are necessary to achieve the outcomes of the research.