Characterization of immune cell subtypes in three commonly used mouse strains reveals gender and strain-specific variations

Abstract

The lack of consensus on bone marrow (BM) and splenic immune cell profiles in preclinical mouse strains complicates comparative analysis across different studies. Although studies have documented relative distribution of immune cells from peripheral blood in mice, similar studies for BM and spleen from naïve mice are lacking. In an effort to establish strain- and gender-specific benchmarks for distribution of various immune cell subtypes in these organs, we performed immunophenotypic analysis of BM cells and splenocytes from both genders of three commonly used murine strains (C57BL/6NCr, 129/SvHsd, and BALB/cAnNCr). Total neutrophils and splenic macrophages were significantly higher in C57BL/6NCr, whereas total B cells were lower. Within C57BL/6NCr female mice, BM B cells were elevated with respect to the males whereas splenic mDCs and splenic neutrophils were reduced. Within BALB/cAnNCr male mice, BM CD4+ Tregs were elevated with respect to the other strains. Furthermore, in male BALB/cAnNCr mice, NK cells were elevated with respect to the other strains in both BM and spleen. Splenic CD4+ Tregs and splenic CD8+ T cells were reduced in male BALB/c mice in comparison to female mice. Bone marrow CD4+ T cells and mDCs were significantly increased in 129/SvHsd whereas splenic CD8+ T cells were reduced. In general, males exhibited higher immature myeloid cells, macrophages, and NK cells. To our knowledge, this study provides a first attempt to systematically establish organ-specific benchmarks on immune cells in studies involving these mouse strains.This study evaluated both innate and adaptive cell types of myeloid and lymphoid lineage from both genders of three major immunocompetent mouse strains used in pre-clinical research. Results of the study underscore that both innate and cell-mediated immune profile varies dramatically based on mouse strain and gender, which will significantly impact on interpretation of experimental outcome in a wide spectrum of studies, including cancer.