bims-hummad 2025-11-23 papers

Front Immunol. 2025 ;16 1699385

Development of an immunodeficient mouse that allows for conditional ablation of monocytic cells.

Alvin J Hui, Kelly Lai, Eva H Doyle, Guadalupe Rivera-Torruco, Alan G Gutierrez, Emily J Du, Yarah B M Meijer, Gabrielle Smith, Renata Gilfanova, Kenton G Chung, Kirsten M Auclair, Pamela Milani, Rachael P Jackman, Johnson Q Tran, Marcus O Muench.

Background and aims: Immunodeficient mice, like the NOD-SCID-Gamma (NSG) strain, are important for the study of xenogeneic cells because of their lack of lymphocytes, dysfunctional hemolytic complement factor 5 (C5), and macrophage defects making them permissive hosts. Nonetheless, cellular barriers remain that limit engraftment of foreign cells such as monocytic phagocytes. Accordingly, we created a line of mice that allows for depletion of monocytic cells by breeding NSG mice with macrophage Fas-induced apoptosis (MaFIA) mice resulting in a stable line of NSG-MaFIA mice.
Methods: NSG-MaFIA mice were generated by crossing NSG and MaFIA mice, with the hybrids backcrossed for nine generations to NSG mice. Flow cytometry was used to detect the expression of the MaFIA gene construct among blood leukocytes. Functional and confirmatory studies evaluated the successful transfer of the MaFIA transgene into the NSG genetic background. Apoptosis of monocytic cells was achieved through administration of a homodimerizer drug. The phenotypic characteristics of NSG mice were confirmed in NSG-MaFIA mice by flow cytometry, CBC analysis, testing of radiation sensitivity, and sequencing of the C5 gene. The permissiveness of NSG-MaFIA mice for xenogeneic engraftment was tested by transfusion of human red blood cells (RBCs) and peripheral blood mononuclear cells (PBMCs).
Results: The MaFIA transgene was hybridized into NSG mice as exhibited by expression of a fluorescent marker. Functional expression of the MaFIA transgene was evidenced by weight loss and decreased fluorescence after homodimerizer treatment. NSG-MaFIA mice are lymphopenic, are sensitive to X-ray irradiation, and carry a mutated C5 gene. Transfusion of human RBCs resulted in similar clearance in NSG and NSG-MaFIA mice, without homodimerizer treatment, indicating a similar innate immune response. Moreover, transfusion of human RBCs or PBMCs after depletion of monocytic cells led to prolonged circulation of RBCs and rapid engraftment of leukocytes.
Conclusions: A novel NSG-MaFIA mouse line was developed that has use in the study of monocytic cells and in the development of better humanized mouse models. Transfusion of human blood cells into cell-depleted NSG-MaFIA mice increased the persistence of the human cells in the circulation, indicating a role for monocytic cells in the removal of xenogeneic cells from immunodeficient mice.

Keywords: blood cell transfusion; cell chimeras; hemolytic complement; humanized mice; macrophage - cell; myeloid cells; phagocyte; xenotransplantation

DOI: https://doi.org/10.3389/fimmu.2025.1699385

Vet Pathol. 2025 Nov 19. 3009858251391388

Characterization of host immune cell infiltrate in human CAR T cell-mediated xenogeneic graft versus host disease in NSG mice.

Elinor Willis, Esha Banerjee, Jillian Verrelle, Arin Cox, Charles-Antoine Assenmacher, Enrico Radaelli.

Chimeric antigen receptor (CAR) T cells are revolutionary cancer therapies that are Food and Drug Administration-approved for hematologic malignancies and under investigation for solid tumors. The use of allogeneic over autologous CAR T cells offers advantages, including broader availability and reduced costs. However, allogeneic CAR T cells frequently trigger graft versus host disease (GvHD), a complication observed in patients and experimental models where human CAR T cells are delivered into immunocompromised mice. To understand the contribution of the mouse immune response to human CAR T cell-mediated xenogeneic GvHD, we analyzed GvHD lesions in a human xenograft tumor model in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice. The animals were treated with second-generation CAR T cells targeting a human tumor-specific antigen without a murine homolog. Mice treated with CAR T cells had more severe GvHD lesions than control mice receiving nontransduced (NT) T cells. Also, tumor burden was negatively correlated with GvHD lesion severity. Immunohistochemical characterization of the GvHD lesions showed that approximately 45% of the immune cell infiltrate consisted of murine cells, most of which were IBA1+ histiocytes, with a small population of CD11c+ dendritic cells. The murine histiocytes expressed activation/antigen presentation markers, including high levels of the costimulatory molecule CD86. Analysis of macrophage polarization indicated an M2-like phenotype. These findings demonstrate a significant contribution of the mouse histiocytic compartment to lesions of human CAR T cell-mediated xenogeneic GvHD. Our results suggest that CD86+ murine antigen-presenting cells help trigger and sustain the xenoreactive CAR T cell response. Furthermore, xenogeneic GvHD exhibits a shift toward M2 polarization in murine macrophages.

Keywords: CAR T cell; NSG mice; graft versus host disease; immunohistochemistry; macrophage polarization; xenogeneic

DOI: https://doi.org/10.1177/03009858251391388

Vet Pathol. 2025 Nov 21. 3009858251386916

Techniques to study chimerism at the tissue level in humanized mice.

Arin Cox, Esha Banerjee, Jillian Verrelle, Elinor Willis, Charles-Antoine Assenmacher, Giovanni Finesso, James C Tarrant, Enrico Radaelli.

Understanding the origin, distribution, and biology of different cell populations in chimeric mice is critical for interpreting the pathological changes developed in these models. To this aim, the methodological work presented here illustrates the validation and application of a collection of labeling techniques to differentiate between specific mouse and human tissue/cell components in formalin-fixed paraffin-embedded samples from chimeric mice, especially those bearing human tumor and immune cells. First, broad approaches to identify cells of human origin using ubiquitous immunohistochemical targets such as HLA-A, Ku80, and human mitochondrial 60 kDa protein (hMito) were established using specimens from humanized mice and a human tissue microarray including both normal and neoplastic samples. Due to its crisp membranous immunoreactivity, HLA-A was the most useful marker for visual human cell identification; however, Ku80 and hMito may be suitable options when HLA-A is not expressed in the cells of interest. Importantly, using one or more of these markers provides a broad range of coverage for the vast majority of human-derived cells in chimeric mice. Second, tailored immunohistochemical or in situ hybridization methodologies to distinguish specific human or mouse cell subsets are presented, focusing on immune/inflammatory cells and human chimeric antigen receptor (CAR) T-cells. These diverse approaches are accompanied by descriptions of case examples highlighting practical diagnostic and experimental applications in the context of various humanized mouse models. While not comprehensive, this work represents a valuable starting reference for pathologists and investigators working with humanized mouse models and seeking to add spatial resolution to the complex landscape of chimeric tissues.

Keywords: chimeric mice; humanized mice; immunohistochemistry; mouse models; xenografts

DOI: https://doi.org/10.1177/03009858251386916