Reconstitution of functional human B lymphocytes in NOD/SCID mice engrafted with ex vivo expanded CD34(+) cord blood cells

Hematopoietic repopulating ability of CD34⁺ progenitor cells ex vivo expanded with different cytokine combinations

Ex-vivo expansion technologies were developed for application of hematopoietic stem cells (HSCs) derived from cord blood (CB). The cytokine combination was essential to expand HSCs ex vivo and maintain the function of expanded HSCs. However the optimal cytokine combination was not determined. In this study, two combinations of cytokines were applied in ex-vivo expansion of HSCs to investigate the effect on the hematopoietic repopulating ability of expanded HSCs. CB CD34(+) cells were expanded with SCF + TPO + FL (STF) or SCF + TPO + FL + IL-3 + IL-6 (STF36) for 7 days and got 30.3 ± 6.4 and 39.8 ± 7.3 folds of total cells, respectively. The cells cultured by both STF and STF36 could engraft and repopulate in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice effectively; however, the STF group achieved higher level of engraftment. These result demonstrated that the cytokine combination of STF36 favored the expansion of cells, while the cytokine combination of STF facilitated the engraftment and multi-lineage repopulating in vivo. These findings may have important implications for the cell therapy.

Antigen-specific antibody production of human B cells in NOG mice reconstituted with the human immune system

Passive antibody administration shows strong potential as a new therapeutic method. In clinical applications, human-derived antibodies with antigen specificity are more useful without putting individuals at risk. Production of human-derived antibodies against given antigens can be obtained from animal models if the human immune system is established in the animals. In fact, past reports revealed that human T and B cells develop from hematopoietic progenitor cells in immunodeficient mice. However, there have been few reports on sufficient induction of antigen-specific antibodies, particularly IgG, in immunodeficient mice reconstituted with human immune cells. In this chapter, we discuss a major shortcoming of induction of antigen-specific IgG antibodies in human immune cells developed in the murine environment based on our data. We demonstrated that human T cell development is restricted by the murine MHC and consequently T cells may not achieve cognate interaction with human B cells. Human B cells developed in the mouse are mainly CD5+B1 cells that preferentially produce IgM. At the same time, human LN transplantation on the spleen enabled NOG mice to produce antigen-specific IgG antibody. These results suggest that if efficient cognate interaction mediated by a certain antigen on MHC class II between human T and B-2 cells occurs, human B cells can produce IgG antibody against a given antigen in the murine environment.

A conserved gene family encodes transmembrane proteins with fibronectin, immunoglobulin and leucine-rich repeat domains (FIGLER)

BACKGROUND

In mouse the cytokine interleukin-7 (IL-7) is required for generation of B lymphocytes, but human IL-7 does not appear to have this function. A bioinformatics approach was therefore used to identify IL-7 receptor related genes in the hope of identifying the elusive human cytokine.

RESULTS

Our database search identified a family of nine gene candidates, which we have provisionally named fibronectin immunoglobulin leucine-rich repeat (FIGLER). The FIGLER 1-9 genes are predicted to encode type I transmembrane glycoproteins with 6-12 leucine-rich repeats (LRR), a C2 type Ig domain, a fibronectin type III domain, a hydrophobic transmembrane domain, and a cytoplasmic domain containing one to four tyrosine residues. Members of this multichromosomal gene family possess 20-47% overall amino acid identity and are differentially expressed in cell lines and primary hematopoietic lineage cells. Genes for FIGLER homologs were identified in macaque, orangutan, chimpanzee, mouse, rat, dog, chicken, toad, and puffer fish databases. The non-human FIGLER homologs share 38-99% overall amino acid identity with their human counterpart.

CONCLUSION

The extracellular domain structure and absence of recognizable cytoplasmic signaling motifs in members of the highly conserved FIGLER gene family suggest a trophic or cell adhesion function for these molecules.

Development of human–human hybridoma from anti-Her-2 peptide–producing B cells in immunized NOG mouse

OBJECTIVE

Numerous monoclonal antibodies have been developed for the purpose of medical treatments, including cancer treatment. For clinical application, the most useful are human-derived antibodies. In this study, we tried to prepare designed antigen-specific antibodies of completely human origin using immunodeficient mouse.

METHODS

Nonobese diabetic/severe combined immunodeficient/IL-2 receptor gamma null mouse (NOG) mouse was used to reconstitute the human immune system with umbilical cord blood hematopoietic stem cells (CB-NOG mouse) and to prepare human-derived Her-2-epitope-specific antibodies. Hybridoma lines were prepared by fusing the human myeloma cell line Karpas707H.

RESULTS

Serum of immunized NOG mouse contained human-derived immunoglobulin M (IgM) antibodies specific for a short peptide sequence of 20 amino acids, including the epitope peptide of apoptotic Her-2 antibody CH401. Hybridoma lines were successfully prepared with spleen B cells obtained from the immunized CB-NOG mouse. One of these cell lines produced human IgM against the epitope peptide that can recognize surface Her-2 molecule.

CONCLUSION

We could produce human-derived IgM antibody against Her-2 epitope peptide in CB-NOG mouse, succeeding in generation of human hybridoma-secreting IgM against a given peptide.

Complex nature of the human antisperm antibody response in SCID mice

Human peripheral blood mononuclear (PBMs) cells were introduced into the peritoneal cavity of severely-combined immunodeficient (SCID) mice in concentrations of 2.5-4.0 x 10(7) cells per mouse. Whole mononuclear cell suspensions were used either unstimulated or following primary in vitro culture with human spermatozoa. In some experiments, immunodepletion of CD8(+) cells was carried out prior to grafting. Lymphocytes were obtained from nonsensitized (to antigen) human subjects or from individuals who were primed in vivo (vasectomized individuals in case of sperm antigens). An enzyme-linked immunosorbent assay was employed to assess total human immunoglobulin (G or M) levels as well as the specificity of the antibodies generated. We have been successful by generating primary and secondary immune responses with 'naïve' human lymphocytes, challenged with chlamydia or ovalbumin but without adjuvant or CD8(+) immunodepletion; however, we were unable to induce specific antibodies to spermatozoa under this regime in SCID male mice. We then employed female SCID mice, treated with sperm antigen extracts (glycosylated or deglycosylated) encapsulated in liposomes and human lymphocytes obtained from 'naïve' or pre-sensitized in vivo subjects. It was found that the most pronounced humoral response to sperm antigens was obtained with deglycosylated antigens and PBMs from vasectomized (in vivo pre-primed to spermatozoa) individuals. A presented SCID mice model can be helpful at understanding of antisperm antibody development and the molecular nature of generated antibodies to modified sperm antigenic entities.

Cotransplantation of third-party mesenchymal stromal cells can alleviate single-donor predominance and increase engraftment from double cord transplantation

Although the infusion of umbilical cord blood (UCB) from multiple donors can be a strategy to overcome the cell dose limitation frequently encountered in UCB transplantation, clinical trials have revealed that cells from one donor dominate engraftment. To investigate the origin of and the factors influencing this inequality, we performed mixed transplantation of 2 UCB units with varying degrees of HLA disparities into NOD/SCID mice and determined donor origins by polymerase chain reaction-sequence-specific oligonucleotide probe (PCR-SSOP) or real-time quantitative (RQ)-PCR for human short tandem repeats (STRs). When total mononuclear cells from 2 units were transplanted as a mixture, cells from one donor predominated (ratio, 81:19), despite comparable overall engraftment when infused as single units, and no augmentation in overall engraftment was observed when compared with the single-unit controls. However, lineage depletion or cotransplantation of mesenchymal stromal cells (MSCs) expanded from third-party bone marrow resulted in more balanced coengraftment. Direct comparison of double UCB transplantation in the presence or absence of MSCs showed that the reduced deviation in the donor ratio (1.8:1 vs. 2.8:1) correlated with a higher overall level of engraftment with MSC cotransplantation. These results indicate that third-party MSCs can be used to alleviate donor deviation and to facilitate engraftment of multidonor UCB.

Functional CD5+ B cells develop predominantly in the spleen of NOD/SCID/gammac(null) (NOG) mice transplanted either with human umbilical cord blood, bone marrow, or mobilized peripheral blood CD34+ cells

OBJECTIVE

Human CD5+ B cells are the major B cell subset in fetal spleen and umbilical cord blood (CB), and their number gradually diminishes in both spleen and peripheral blood from infancy through childhood while conventional B cells increase. In this study, we investigated whether CD5+ cells differentiate from adult hematopoietic stem cells (HSCs) as well as fetal ones in immunodeficient mice.

METHODS

In our system, NOD/SCID/gammac(null) (NOG) mice were transplanted with CD34+ cells from CB (hCB model), adult bone marrow (hBM model), and mobilized peripheral blood (hMPB model).

RESULTS

In these model mice, a high proportion of CD19+IgM+CD5+ mature B cells appeared in the spleen, regardless of the CD34+ cell origin, 4 to 8 weeks after transplantation, while the majority were CD19+IgM-CD5- immature B cells in BM. The CD19+CD5- BM cells showed to express CD5 after the coculture with NOG spleen cells. In the sera of immunized hCB model mice with DNP-KLH, antigen-specific IgM but not IgG was enhanced.

CONCLUSION

Our results show that adult CD34+ cells develop into functional CD5+ B cells in NOG spleen as much as fetal CD34+ cells do.