We present a detailed analysis of the content and organization of the human immunoglobulin VH locus. Human VH genes representing five distinct families were isolated, including novel members belonging to two out of three of the known VH gene families (VH1 and VH3) as well as members of three new families (VH4, VH5, and VH6). We report the nucleotide sequence of 21 novel human VH genes, many of which belong to the three new VH gene families. In addition, we provide a preliminary analysis of the organization of these gene segments over the full extent of the locus. We find that the five multi‐segment families (VH1‐5) have members interspersed over nearly the full 1500‐2000 kb of the VH locus, and estimate that the entire heavy chain locus covers 2500 kb or less. Finally, we provide the first report of the physical linkage of the variable and constant loci of a human Ig gene family by demonstrating that the most proximal known human VH segments lie within 100 kb of the constant region locus.

We have studied frequencies of VH gene utilization in a panel of monoclonal Epstein-Barr virus (EBV)-transformed B cell lines derived from human adult and fetal tissues as well as in monoclonal B cells obtained from fresh chronic lymphocytic leukemia (CLL) samples. The results show that IgM-secreting EBV cell lines from both fetal and adult tissues utilize VH genes from particular families roughly in proportion to estimated family size, suggesting that the repertoire of sigM-positive B cells in both fetal and adult organs is 'normalized' with respect to the V(H) gene family. In contrast, we find a highly biased pattern of VH gene expression in CLLs. The significance of these findings is discussed in the context of mechanisms that could be involved in normal B cell repertoire development and in the process of malignant transformation of precursors of CLL.

Preferential usage of JH-proximal VH genes has been demonstrated in immature murine B cell repertoires. To determine whether this phenomenon is also evident in human repertoires, we studied utilization of VH6, the most JH-proximal human VH gene. Examination of VH gene usage in a panel of precursor B cell acute lymphoblastic leukemia samples indicated that 15% of the IgH rearrangements utilized VH6. VH6 is a single-member family in a total repertoire of 100-200 VH genes; thus, if usage were purely random, one would expect VH6 rearrangement frequency to be less than 1%. Analysis of VH gene usage in normal lymphoid tissues also revealed biased usage of VH6. VH6 was preferentially utilized in 16- to 24-week-old fetal liver as compared to adult peripheral blood mononuclear cells or spleen. Possible implications of the conservation of preferential usage of JH-proximal genes in both immature murine and human repertoires are discussed.