Characterization of the CDR3 region of rearranged alpha heavy chain genes in human fetal liver

Abstract

The human fetal liver is an early site for B cell development. Pre B cells are first detectable in human fetal life at 8 weeks of gestation, when the rearrangement of the mu heavy chain genes starts. In this study we characterize the CDR3 region of rearranged alpha heavy chain transcripts from four human fetal livers ranging from 8 to 11 weeks of gestation. Each fetal liver showed a limited number of variations in CDR3 sequences compared with adult peripheral blood mononuclear cells (PBMC). Sequence analysis of 91 clones demonstrated that there was no preference for the usage of a certain JH gene segment, whereas a preference for usage of DH family genes, DXP and DLR, was seen in most cases during early fetal life. This is the first study where rearranged alpha heavy chain genes in fetal liver have been characterized. Our data suggest that the usage of JH genes is random, while there is a preference for DH family genes in human fetal liver.

Fig. 1

The complete CDR3 region of all sequenced clones from human fetal liver and adult peripheral blood mononuclear cells (PBMC). Each sequence starts with the end of FR3 of the V_H gene. The numbers in parentheses after each fetal liver clone indicate the numbers of identical clones that have been sequenced. Identified D and J_H genes are specified in parentheses.