Humanized Mouse Models

NSG® and NSG®-SGM3 mice are a proven host for engraftment of human tumors or establishment of human immunity following hematopoietic stem cell transplantation. Understanding the interactions between human immune cells and tumors is paramount when devising treatment strategies that prevent tumor evasion of immune cells and improve cytotoxic responses.

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Charles River's expertise in oncology drug discovery, spanning from target identification to IND studies, makes us ideally suited to run your humanized mouse tumor model studies for you.

 

Frequently Asked Questions (FAQs) Regarding Humanizing the NSG® Mouse

  • Do NSG™ mice require irradiation before injecting PBMCs?

    No. Only hematopoietic stem cells require preconditioning irradiation for efficient engraftment. Irradiation accelerates the GVHD response.

  • What is graft-versus-host disease? When does it occur?

    Graft-versus-host-disease (GVHD) occurs when mature immune cells mount an immune attack on the mouse. This is a possibility any time the immune cells are sourced directly from human blood (PBMCs). It also happens when mature mouse immune cells are injected, if the cells come from any strain with a major histocompatibility complex (MHC) haplotye that is not matched to NOD/ShiLt. GVHD usually sets in within 3-4 weeks after injection of human PBMCs. NSG® mice without MHC class I show delayed onset of GVHD.

  • Why do NSG® mice require irradiation before hematopoietic stem cell engraftment?

    Treatment with radiation (usually from an X-irradiator or a cesium source) is a prerequisite for efficient colonization of mouse bone marrow by human hematopoietic stem cells. Irradiation works by killing the mouse stem cells and opening the bone marrow niche, and also by inducing expression of cytokines like Kit ligand (also known as stem cell factor, or SCF). The preconditioning irradiation dose depends on the age of the mouse and often needs to be optimized in every laboratory. Newborn mice tolerate lower doses than juvenile or adult mice.

  • How long can a CD34-humanized NSG® mouse remain engrafted with human immune cells?

    CD45+ cells (mature white blood cells) have been detected in the peripheral blood as long as one year after injection with CD34+ hematopoietic stem cells. It has been found that there are no signs of graft-versus-host disease when T-cell-depleted stem cells are sourced from cord blood in mice for up to one year post-engraftment.

  • How functional is the human immune system that develops in a CD34-injected NSG®?

    The different cell types that make up the lymphoid and myeloid lineages are present within humanized NSG® mice, and there is a significant amount of effort going into understanding how functional they are. Here’s a summary of some key findings:

    • The T cell repertoire is diverse and can participate in delayed type hypersensitivity responses.
       
    • B cells are present and can show some immune responses, although they are not especially robust because of the absence of human cytokines that support this lineage.
       
    • The functions of the NK cells, neutrophils, red blood cells, and other cells of the myeloid lineages have all been published.
       
    • The humanized immune system is capable of rejecting HLA-mismatched human pancreatic islet transplants as well as mouse skin grafts.
  • When can a humanized NSG® mouse be used for vaccine studies?

    To function in a vaccine model, the human T cells in the mouse must be able to interact efficiently with human antigen presenting cells, such as dendritic cells. This phenomenon is known as “HLA restriction” (HLA is the human counterpart to the mouse MHC). Unless the human T cells have developed in a transgenic mouse expressing human HLA, or in a mouse with a human thymus implant, then the interactions are not efficient, and the humanized immune system is probably not capable of mounting an efficient immune response to a vaccination.

  • Where can I find protocols describing humanized NSG® mice?

    These publications describe protocols and considerations for creating humanized NSG™ mice. Pearson, et al. 2008 is especially recommended:

  • How are humanized mouse models created?

    The NSG model's immune system is humanized by irradiating and destroying the host immune system. Once the immune system is knocked out, human PBMCs are injected to create a humanized model. Engrafted human cells can be detected as early as 10 days after the PBMC injection.

    Humanized Mice

    Humanized mouse models can be used for tumor models to screen cancer therapies in an intact human immune system.
    Schematic of humanized mouse tumor models. The mouse immune systems are humanized by irradiating and destroying the host immune system and introducing human immune cells.

  • What are humanized mice used for?

    Humanized mouse models are used to compare tumor therapies, study the human immune system, and to study the function of genes in healthy and diseased models.