Gene targeting strategy for B-NDG B2m plus/hIL15 mice. The murine B2m gene was knocked out while a fused gene composed of murine B2m and Fcgrt gene was inserted after the signal peptide sequence of murine Fcgrt gene in B-NDG B2m plus/hIL15 mice. Meanwhile, The CDS region of human IL15 gene was inserted after the 5′UTR of the mouse Il15 gene in B-NDG B2m plus/hIL15 mice.

Strain specific MHC I molecule H-2K^d expression analysis in homozygous B-NDG B2m plus/hIL15 mice by flow cytometry. Splenocytes and bone marrow cells were collected from B-NDG mice and homozygous B-NDG B2m plus/hIL15 mice, and analyzed by flow cytometry with species-specific anti-H-2K^d antibody. Mouse H-2K^d was detectable in B-NDG mice but not in homozygous B-NDG B2m plus/hIL15 mice. The result demonstrates that because of B2m gene knockout, mouse MHC I molecule was not expressed in B-NDG B2m plus/hIL15 mice.

Strain specific IL15 expression analysis in homozygous B-NDG B2m plus/hIL15 mice by ELISA. Serum was collected from B-NDG mice and homozygous B-NDG B2m plus/hIL15 mice which were stimulated with poly(I:C) in vivo, and analyzed by ELISA with species-specific anti-hIL15 antibody. Human IL15 was detectable in homozygous B-NDG B2m plus/hIL15 mice but not in B-NDG mice.

Engraftment of human PBMC in B-NDG B2m plus/hIL15 mice alleviated GvHD and enhanced reconstitution of human NK cells. Female B-NDG mice and B-NDG B2m plus/hIL15 mice were respectively engrafted intravenously with human PBMCs on day 0 (n=6). Peripheral blood was collected to analyze the reconstitution level of human immune cells by FACS. A. Survival rates of the mice were analyzed with Kaplan Meier survival curves. B. Body weight changes. C. Cell number analysis of hCD45+ cells, hCD3+ cells and hCD56+ cells by FACS. D. Representative FACS plots. Results showed that B-NDG B2m plus/hIL15 mice can significantly extend the life span and reduced the GvHD induced with human PBMC engraftment when compared that in B-NDG mice. Human CD3+ cells and CD56+ cells can be reconstituted successfully in B-NDG B2m plus/hIL15 mice. B-NDG B2m plus/hIL15 mice are suitable mouse model for human T cell and NK cell reconstitution with PBMC engraftment. Values were expressed as mean ± SEM.