Background The NCG is a triple immunodeficient mouse that lacks mouse T cells, B cells and NK cells. This makes it permissible to engraftment by human hematopoietic stem cells. Immune humanized mice are a unique research model that has been used extensively to study the effects of immunotherapies but myeloablation is required for human hematopoietic stem cells to engraft. Radiation or chemoablation can cause background changes and can often negatively impact bodyweight, behavior, and rates of survival. The NCG-X model was developed to circumvent these issues by editing the kit gene leading to a lack of function allowing for humanization without the unwanted effects of radiating the mouse.

Methods NCG-X mice were genetically modified from the NCG mouse strain (NOD-Prkdc^em26Cd52Il2rg^em26Cd22 /NjuCrl) to produce a mouse that lack functional kit. 5–7-week-old NCG-X mice were engrafted with cord blood-derived cord-blood derived human hematopoietic stem cells without the use of any form of myeloablation and compared to NCG mice irradiated with a sublethal dose of total body irradiation. Peripheral blood was collected from immune humanized mice to examine human cell populations.

Results Humanized NCG-X mice had similar levels of engraftment of human CD45⁺ cells as well as human CD3⁺ and human CD19⁺ cells without irradiation compared to irradiated humanized NCG mice.

Conclusions The humanized NCG-X exhibit similar levels of humanization and immune cell subpopulations compared to the humanized NCG. This allows for evaluation of immunotherapy without the effects of radiation on the mouse tissue.

Ethics Approval Animal procedures were reviewed and approved by CRL IACUC and performed in an AAALAC accredited facility.