{'fraction_non_alphanumeric': 0.022810890360559236, 'fraction_numerical': 0.020603384841795438, 'mean_word_length': 5.017699115044247, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 1, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Development of VH81X transgene-bearing B cells in fetus and adult: sites for expansion and deletion in conventional and CD5/B1 cells.

The most D-proximal functional VH gene, VH81X, is preferentially expressed in the mouse fetal B cell repertoire; however, it is expressed in few B cells in the adult. To determine when VH81X gene expression affects size and phenotype of particular stages in B cell differentiation, transgenic mice have been developed expressing a germline fetal liver-derived VH81X-mu rearrangement. Comparative analysis of B lymphopoiesis reveals similarities and differences between fetal liver and adult bone marrow which pinpoint developmental stages in mice during which VH81X-expressing B cell progenitors expand or deplete compartment sizes. These include a similar reduction in c-kitR+ and establishment of a predominant CD43low/HSAhigh phenotype within the B220+ CD43+ compartment which is dependent on the association of the transgene with lambda 5. In contrast, the CD43- pre-B and immature B cell compartments are expanded in the fetus but not in the adult. In addition, there are other factors that later disfavor the survival of VH81X-expressing B1 and B2 cells. Thus the failure to detect VH81X-bearing B cells in the adult is the result of a multistep selection process occurring at all stages during B repertoire expansion.