Selective expression of a VHIV subfamily of immunoglobulin genes in human CD5+ B lymphocytes from cord blood.

Abstract

During the past few years, heterogeneity within B lymphocyte populations has become increasingly apparent. Several studies have demonstrated functional, physiological, and developmental heterogeneity. Studies in the mouse suggested that two separate lineages of B cells may exist (1) . One lineage, is defined by cell surface expression of the Ly-1 antigen, characteristic of T lymphocytes, and the secretion of polyspecific antibodies reactive with a variety of self antigens. The second lineage lacks the Ly-1 antigen and produces antibodies, mainly, to exogenous antigens (1). It is not clear, however, if the distinction is also reflected in antibody variable region gene use by the Ly-1 + and Ly-1 -B cell subsets. This question can be approached by analysis ofvariable region gene segment rearrangements, at the DNA level or through serological markers expressed on the protein products.In humans, the majority of B lymphocytes in fetal liver, cord blood, and a minority in adult peripheral blood and lymph nodes express surface CD5 molecule, the human equivalent of mouse Ly-1 (2) . 109In the present study, we have used a number ofmAbs that recognize cross-reactive idiotypes (CRI)t associated with individual V or V, gene family products to examine IgV gene use in CD5+ and CD5 -B lymphocytes . Materials and MethodsPreparation and Sorting of B Lymphocytes. B Lymphocytes were enriched from heparinized blood of three full-term donors by centrifugation over Ficoll-Hypaque and rosetting using SRBCs (3). The enriched B cell populations were stained simultaneously with fluorescein-conjugated anti-CD20 (clone Leu-16) and PE-labeled anti-CD5 (clone Leu-1) and sorted using a FACStar® (Becton Dickinson Immunocytometric Systems, Mountain View, CA). Lymphocytes displaying green fluorescence only (CD20', CD5 -cells) and those displaying green and red fluorescence (CD20', CD5' cells) were gated and sorted as CD5 -and CD5+ B cells, respectively.'Abbreviation used in this paper: CRI, cross-reactive idiotypes.J . Exp. Med .

Regulation of inherently autoreactive VH4-34 B cells in the maintenance of human B cell tolerance

“…It is therefore tempting to speculate that the underrepresentation of VH4-34 cells in germinal centers and germinal center-derived B cells and plasma cells could be the result of their positive selection into a separate anatomic and functional compartment, perhaps a human "B1-like" compartment. Such interpretation is consistent with the observation that VH4-34 antibodies are frequently made by human cord blood CD5 + B cells but are absent from CD5 -cells (64). Yet, this dichotomy is not preserved in the adult and singlecell PCR analysis of adult IgM B cells has demonstrated similar expression of VH4-34 in CD5 + and CD5 -cells (65).…”

Loss of a chromosomal region with synteny to human 13q14 occurs in mouse chronic lymphocytic leukemia that originates from early-generated B-1 B cells

“…As in human cord blood, CD5 + B cells are present in early in life in normal mice 13, 36, 37 . One day after birth in ON25 mice (heterozygous knock-in), nearly all newly generated immature B cells in the liver expressed the V H Q52id + μ heavy chain, most with a κ light chain (Figure 2e top).…”

“…However, the differential expression patterns of Lin28b that distinguishes fetal and adult hematopoietic cells in mice has also been found in humans 17 , and CD5 + B cell generation, including at the immature stage, is the predominant outcome of development in the human fetus and in cord blood 36, 37, 59 . Since the level of TdT is lower in human fetal development than adult, but is upregulated much earlier than in mice 60 , N-addition in human V H 1-69/D3-16/J3 with a longer CDR3 does not exclude fetal/neonatal generation.…”

Immunoglobulin Genes in Autoimmunity

“…Nucleotide sequence analysis of the VH and VL monoreactive high affinity of an IgG anti-DNA antibody secreted by a monoclonal (T14) from an EBV-transformed B cell line from a patient with active SLE showed that V,,T14 is 94.8% homologous with the germline VH4.21 gene segment and VLT14 is 98.6% ho mologous to the germline kv325 gene segment of the VkI I lb subfamily [34], Comparison of the VM 4T14 and VkIIIb.T14 and their respective germlinc genes showed a nonrandom distribution of silent and replacement muta tions in the combined CDR region, supporting the process of antigen-driven B cell activation and selection. Interest ingly, kv325 is also known to be overrepresented in ne oplasms that commonly bear the CD5 antigen and in Epstein-Barr virus (EBV)-transformcd cell lines derived from CD5+ cord blood cells [41,42]; the gene segment en coding T14 shows a striking overlap with those frequently expressed in natural anti-DNA antibodies [34].…”