NSG Mice: Genetics, Research Uses, and Lab Care

Short answer

NSG mice (NOD.Cg-Prkdc^scid Il2rg^tm1Wjl/SzJ, commonly known as NOD scid gamma mice) are severely immunodeficient laboratory animals lacking mature T cells, B cells, and functional natural killer (NK) cells. Developed at The Jackson Laboratory, the strain features high affinity between murine SIRPα and human CD47, enabling superior human cell and tissue engraftment for oncology and immunology.

Definition and scope

The term NSG mouse refers to an inbred immunodeficient laboratory strain designated NOD.Cg-Prkdc^scid Il2rg^tm1Wjl/SzJ (The Jackson Laboratory stock number 005557), commonly termed NOD scid gamma or NOD scid gamma mice. The model integrates three genetic components:

• Non-Obese Diabetic (NOD/ShiLtJ) background: Contributes innate immune defects, including impaired macrophage function, absent hemolytic complement (natural 2-bp deletion in C5), and a polymorphic Sirpa allele. Murine SIRPα on NOD macrophages binds human CD47 with high affinity, delivering an inhibitory signal that prevents phagocytosis of engrafted human cells.
• Severe combined immune deficiency (scid) mutation: A loss-of-function mutation in Prkdc^scid on chromosome 16. Disabling non-homologous end joining during V(D)J recombination blocks antigen receptor gene assembly, abolishing mature T and B lymphocytes.
• IL-2 receptor common gamma chain null mutation (Il2rg^tm1Wjl): An X-linked targeted deletion of the common gamma subunit (IL-2Rγ or CD132) shared by IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21. Blocking IL-15 signaling prevents natural killer (NK) cell development.

Unlike classic NOD-scid mice, NSG mice lack scid-associated leakiness (the spontaneous generation of oligoclonal lymphocytes) and remain resistant to thymic lymphomas, supporting a median lifespan exceeding 22 months under barrier housing.

How it works or how it is used in practice

Lacking adaptive immunity and functional NK cells while tolerating human surface antigens, NSG mice serve as the primary host for xenotransplantation and immunology research.

Patient-Derived Xenografts (PDX)

NSG mice are the reference host for patient-derived xenografts (PDX). Surgically resected human tumor tissue implants directly into host tissues without immune rejection, maintaining original histological architecture, stromal interactions, and clonal profiles across early passages. These models support preclinical evaluation of targeted therapeutics, cytotoxic drugs, and resistance mechanisms.

Human Immune System (HIS) Engraftment

The strain provides a recipient platform for humanized models through two standard protocols:

• CD34+ Hematopoietic Stem Cell (HSC) Engraftment: Conditioned NSG mice receive human CD34+ HSCs from cord blood or bone marrow. Stem cells home to the marrow and differentiate over 12 to 16 weeks into functional human B cells, T cells, monocytes, and dendritic cells, supporting long-term studies exceeding 6 months in viral pathogenesis and vaccine efficacy.
• Peripheral Blood Mononuclear Cell (PBMC) Transfer: Injecting adult human PBMCs into unconditioned NSG mice achieves rapid human T-cell engraftment within 1 to 2 weeks for acute evaluation of immunotherapies like CAR-T cells. However, human T cells recognize murine MHC, triggering lethal xenogeneic graft-versus-host disease (xGvHD) within 4 to 8 weeks.

Investigators routinely confirm genetic authenticity through PCR genotyping and monitor human leukocyte chimerism using flow cytometry.

Types or related concepts

Translational researchers choose immunodeficient models based on experimental requirements. In evaluating nsg vs nod scid and athymic strains, teams balance immunodeficiency depth against radiosensitivity and experimental duration.

Model Strain	Genetic Basis	T and B Cells	NK Cells	Macrophage Clearance of Human Cells	SCID Leakiness	Median Lifespan	Primary Research Use
NSG (NOD scid gamma)	NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ	Absent	Absent	Inhibited (NOD SIRPα binds human CD47)	None	≥22 months	CD34+ HSC humanization, PDX oncology, CAR-T assessment
NOD-scid	NOD.CB17-Prkdcscid/J	Absent	Present (functional)	Inhibited (NOD SIRPα binds human CD47)	Present (reversion with age)	~8–9 months (thymic lymphoma)	Short-term cell-line xenografts, limited stem cell transfer
Athymic Nude	Foxn1nu	T cells absent; B cells normal	Present (functional)	Active (murine SIRPα does not suppress phagocytosis)	None	≥18 months	Cell-line-derived xenografts (CDX), radiation studies
NSG-SGM3 (Transgenic Variant)	NSG + human IL3, CSF2, KITLG	Absent	Absent	Inhibited (NOD SIRPα binds human CD47)	None	~9–12 months	Enhanced human myeloid and regulatory T-cell development

Where it matters for labs, clinics or supply decisions

Maintaining an NSG colony requires dedicated micro-environmental controls and strict institutional compliance workflows.

Maximum Barrier Housing and Biosecurity

Because NSG mice lack adaptive and NK cell immunity, opportunistic pathogens like Pneumocystis carinii, Corynebacterium bovis, and Pseudomonas aeruginosa cause rapid, fatal infections. Facilities must enforce strict barrier operations:

• Individually Ventilated Cages (IVC): Housing racks must deliver HEPA-filtered air to microisolator cages under controlled positive pressure.
• Aseptic Handling: Cage changes and animal procedures must occur inside a certified Class II biosafety cabinet or change station using sterile PPE, routine glove changes, and validated disinfectants.
• Sterilized Consumables: Feed must be autoclaved or irradiated. Water must be autoclaved and either acidified (pH 2.5 to 3.0) or chlorinated to prevent opportunistic bacterial proliferation.

Radiation Sensitivity and Pre-Conditioning Precautions

Because the Prkdc^scid mutation impairs DNA double-strand break repair, NSG mice are hypersensitive to ionizing radiation. Conditioning doses for CD34+ cell transfers must be restricted to low levels (typically 1.0 to 2.0 Gy for adults) or replaced with non-genotoxic conditioning agents to prevent lethal gastrointestinal and hematopoietic toxicity.

Institutional Animal Care and Biosafety Oversight

Research using NSG mice and human materials requires coordinated institutional oversight. Protocols must receive approval from an Institutional Animal Care and Use Committee through a formal IACUC protocol specifying tumor burden criteria, body condition scoring, and humane endpoints. Work involving primary human biological specimens or viral vectors also requires Institutional Biosafety Committee review. For operational boundaries, refer to the reference on IACUC and IBC oversight.

Common misunderstandings

Key experimental pitfalls when working with NSG mice include:

• Assuming total absence of immune cells: NSG mice lack mature T cells, B cells, and functional NK cells, but retain murine macrophages, granulocytes, and dendritic cells. While macrophage clearance of human cells is suppressed via CD47-SIRPα binding, innate myeloid cells still respond to microbial patterns and produce inflammatory cytokines.
• Treating NSG and NOD-scid as interchangeable: Classic NOD-scid mice retain functional NK cells, develop scid leakiness with age, and succumb to thymic lymphomas within 8 to 9 months, making them unsuitable for long-term CD34+ humanization or high-efficiency PDX engraftment.
• Equating PBMC transfer with complete humanization: Transferring human PBMCs produces circulating human T cells but inevitably causes lethal xenogeneic graft-versus-host disease (xGvHD) within 4 to 8 weeks, whereas CD34+ HSC reconstitution establishes de novo multi-lineage hematopoiesis.
• Applying standard rodent irradiation protocols: Doses standard for wild-type mice (8 to 10 Gy) are lethal in NSG mice due to defective non-homologous end joining repair.

Frequently asked questions

What does NSG stand for in NSG mice?

NSG stands for NOD scid gamma, reflecting its three genetic foundations: the NOD/ShiLtJ background, the severe combined immune deficiency (scid) mutation in Prkdc, and the common interleukin-2 receptor gamma chain null mutation (Il2rg).

Why do NSG mice engraft human cells more efficiently than other models?

NSG mice lack mature T cells, B cells, and functional NK cells, preventing cell-mediated graft rejection. In addition, the native NOD background possesses a SIRPα receptor that binds human CD47 with high affinity, transmitting an inhibitory signal that prevents host macrophages from phagocytosing human cells.

How long do NSG mice live in research facilities?

Under specific pathogen-free (SPF) maximum barrier conditions, NSG mice have a median lifespan exceeding 22 months. They are resistant to the spontaneous thymic lymphomas that truncate the lifespan of classic NOD-scid mice.

Why are NSG mice sensitive to radiation?

The Prkdc^scid mutation impairs the catalytic subunit of DNA-dependent protein kinase, disabling non-homologous end joining repair of double-strand DNA breaks. As a result, NSG mice cannot repair ionizing radiation damage efficiently and require low pre-conditioning doses.

Sources

• The Jackson Laboratory, JAX Stock No. 005557 — NOD.Cg-Prkdc^scid Il2rg^tm1Wjl/SzJ (NSG) Strain Datasheet (read 2026-11-07).
• Shultz, L. D., Lyons, B. L., Burzenski, L. M., et al., Human lymphoid and myeloid cell development in NOD/LtSz-scid IL2Rγnull mice engrafted with mobilized human hemopoietic stem cells, The Journal of Immunology, 2005, 174(10): 6477–6489 (read 2026-11-07).
• Shultz, L. D., Brehm, M. A., Garcia-Martinez, J. V., and Greiner, D. L., Humanized mice for immune system investigation: progress, promise and challenges, Nature Reviews Immunology, 2012, 12(11): 786–798 (read 2026-11-07).
• National Research Council, Guide for the Care and Use of Laboratory Animals, 8th Edition, National Academies Press, 2011 (read 2026-11-07).