Relatively Normal Human Lymphopoiesis but Rapid Turnover of Newly Formed B Cells in Transplanted Nonobese Diabetic/SCID Mice

Abstract

Human B lineage lymphocyte precursors in chimeric nonobese diabetic/SCID mice transplanted with umbilical cord blood cells were directly compared with those present in normal bone marrow. All precursor subsets were represented and in nearly normal proportions. Cell cycle activity and population dynamics were investigated by staining for the Ki-67 nuclear Ag as well as by incorporation experiments using 5-bromo-2′-deoxyuridine. Again, this revealed that human B lymphopoiesis in chimeras parallels that in normal marrow with respect to replication and progression through the lineage. Moreover, sequencing of Ig gene rearrangement products showed that a diverse repertoire of VH genes was utilized by the newly formed lymphocytes but there was no evidence for somatic hypermutation. The newly formed B cells frequently acquired the CD5 Ag and had a short life span in the periphery. Thus, all molecular requirements for normal B lymphocyte formation are present in nonobese diabetic/SCID mice, but additional factors are needed for recruitment of B cells into a fully mature, long-lived pool. The model can now be exploited to learn about species restricted and conserved environmental cues for human B lymphocyte production.

Human fetal, cord blood, and adult lymphocyte progenitors have similar potential for generating B cells with a diverse immunoglobulin repertoire

“…Pooled cord blood experiments were described previously. 32 A third single donor cord blood transplantation in NOD/SCID mice was also performed. The animals were killed 8 weeks later and 5 lymphocyte subsets were isolated as detailed in "Materials and methods" (and Figure 1A).…”

“…Adult and fetal engrafted samples were treated according to Rossi et al 32 with the addition of a CD34 Magnetic Acquisition Cell Sorting isolation step (Miltenyi Biotec, Auburn, CA) in which CD34 ϩ progenitor cells were separated from CD34 Ϫ cells. In the latter case, 2 ϫ 10 5 CD34 ϩ cells were injected with 5 ϫ 10 6 irradiated (adult bone marrow cells) or unirradiated (fetal bone marrow cells) CD34 Ϫ cells in a volume of 200 L into each irradiated 6-week-old mouse (1 Gy; 4-5 mice per transplantation).…”

“…32,33 Either the TOPO-TA polymerase chain reaction (PCR) Cloning Kit (Invitrogen, Carlsbad, CA) or Qiagen PCR Cloning Kit (Qiagen, Valencia, CA) was used for fetal bone marrow and adult bone marrow engraftment experiments. The following were compared from chimeric mice that underwent transplantation: 240 unique sequences from fetal bone marrow, 571 unique sequences from cord blood (255 of which were reported previously), and 289 unique sequences from adult bone marrow.…”

“…30,31 Indeed, we recently found that all stages of B-cell progenitors were normally represented in the marrow of chimeric mice, and newly formed B cells expressed a diverse repertoire of antigen receptors. 32 A rationale for the present study followed from the fact that the lymphocyte differentiation potential of hematopoietic stem cells from diverse human sources can be compared in a common environment using this model. Here we show that B cells emerging from mice that received transplants of fetal, cord blood, or adult stem cell sources express a comparable immunoglobulin repertoire with respect to VH4 and JH segments and show very similar yet not identical HCDR3 characteristics.…”

Investigating human leukemogenesis: from cell lines to in vivo models of human leukemia

“…79,119,126 This bias toward B lymphopoiesis also appears to impact upon leukemogenesis. In vitro -in vivo crossover studies with Lin-CB cells expressing MLL-ENL have shown that cells with the potential to initiate B-lymphoid and/or myeloid leukemogenic programs are clearly present immediately following transduction, but invariably generate B-ALL when directly transplanted into mice.…”