The analysis of the functions of human B and T cells in humanized NOD/shi-scid/γcnull (NOG) mice (hu-HSC NOG mice)

Abstract

'Humanized mice' are anticipated to be a valuable tool for studying the human immune system, but the reconstituted human immune cells have not yet been well characterized. Here, we extensively investigated the differentiation and functions of human B and T cells in a supra-immunodeficient mouse strain, NOD/shi-scid/gammac(null) (NOG) reconstituted with CD34(+) hematopoietic stem cells obtained from umbilical cord blood. In these hu-HSC NOG mice, the development of human B cells was partially blocked, and a significant number of B-cell progenitors accumulated in the spleen. The mature CD19(+)IgM(+)IgD(+) human B cells of the hu-HSC NOG mice could produce IgG in vivo and in vitro by antigenic stimulation. In contrast, although human T cells with an apparently normal phenotype developed, most of them could neither proliferate nor produce IL-2 in response to antigenic stimulation by anti-CD3 and anti-CD28 antibodies in vitro. The positive selection of human T cells in the thymus was sufficiently functional, if not complete, and mainly mediated by mouse class II, suggesting that the human T cells lost their function in the periphery. We found that multiple mechanisms were involved in the T-cell abnormalities. Collectively, our results demonstrate that further improvements are necessary before humanized mice with a functional human immune system are achieved.

Transgenic expression of human signal regulatory protein alpha in Rag2−/−γc−/−mice improves engraftment of human hematopoietic cells in humanized mice

“…These studies included NSG and BALB/c DKO mice and different adjuvant/antigen combinations. At this point it remains open why antibody production is limited, but because B cells from humanized mice respond normally in vitro, it indicates that the human immune system provides only inefficient help in vivo (44). In hSIRPa-DKO mice, immunization with a T cell-dependent antigen induced stronger immune responses as measured by higher titers of antigen-specific IgM compared with DKO mice.…”

Current advances in humanized mouse models

“…For example, no or rare antigen-specific IgG production occurs after multiple injections of antigens. 25 To overcome this issue, various improved strains based on these immunodeficient mice have been developed or are being developed by several groups, including our group. 34,35 In Figure 1, the history of the development of immunodeficient humanized mice and their respective improvements are summarized.…”

“…23 The significance of this upregulated CD5 expression remains controversial, i.e., whether these are human B-1 cells or transitional 1 B cells. 23,25 Immunization of humanized mice with various exogenous substances induces antigen-specific IgM responses, suggesting that the B-cell repertoire is diverse and can cover a myriad of antigens. 21,23 Since antigen-specific IgG responses in conventional humanized mice are very weak, 14,21,23 it has been speculated that these B cells have some intrinsic defects in the class switch machineries.…”

“…Several in vitro experiments, however, demonstrated that these B cells do produce IgG in response to stimulation through their antigen receptors and CD40 in the presence of IL-21. 25 In addition, recent reports have shown that new mouse strains that express HLA-DR mounted an antigen-specific IgG response upon immunization. 43 Collectively, B cells in humanized mice maintain the ability to mediate humoral immune reactions.…”

“…The differentiation of HSCs into immature human T and B cells and poor interactions between these cells were suggested based on cell phenotype analysis and the rare production of antigen-specific immunoglobulin G (IgG) class antibodies. 25 These results suggest that current immunodeficient mice may be insufficient, and human factors that support the differentiation and maturation of cells and mediate cell-to-cell interactions must be introduced. To this end, a new series of immunodeficient mice has been generated by introducing human cytokine genes into NOD/SCID/cc null , Rag2 null cc null mice.…”