VH4 and JH gene segment use as a function of the source of transplanted hematopoietic precursors. VH4 leader and μ constant region primers were used to amplify VH4 from cDNA derived from each population studied. The products were then cloned and sequences of colony picks were obtained. Data shown represent immunoglobulin genes derived from adult (▪), cord blood (▦), or fetal (□) progenitors. The representation of the VH4 and JH gene segments from sIgM⁺ cells (A,C) and sIgM^- cells (B,D) are shown. Data represent the percent of each family found in 2 experiments for adult bone marrow (sIgM⁺,n = 135 + 36; sIgM^-, n = 50 + 56) and cord blood (sIgM⁺, n = 172 + 129 + 114; sIgM^-, n = 87 + 31 + 43) LP sources and 1 experiment for the fetal LP source (sIgM⁺, n = 188; sIgM^-, n = 53). Because of low numbers, VH4-28 and VH4-30-2 were considered together in statistical tests. The difference in VH4-34 in sIgM^- cells among LP sources is significant for an age-related trend (P = .006) and VH4-31 and VH4-59 in sIgM⁺ cells among LP sources (P = .04 and P = .002) were significant for an age-related trend, but other differences were not significant by Chi square analysis. No significant differences were found in JH gene segments. Error bars indicate standard error.