Rearrangements at the IgH locus

During B cell development, JH rearrangements occur in an ordered fashion. The assembly of D to JH segments precedes VH to DJH joining which can itself be followed by a VH to VHDJH joint (VH replacement Fig. 3). These different rearrangements will be described in detail in the following three sections. 

To understand the biological function of multiple D to JH joinings it is important to realize that all rearrangement events occur in rapidly dividing pre-B cell clones [59,60]. How many different stem cells are giving rise to the pre-B cells generated 

Usage of D and JH segments in unselected VHDJH complexes ([55,68] and Dildrop et al., unpublished) 

Data were obtained from myelomas or hybridomas from B cells activated with bacterial lipopolysac-charide. X, D element used could not be identified. 

Evidence for frequent DJH replacement during B cell development has also been obtained from an analysis of the D and JH usage in VHDJH complexes of myeloma or unselected hybridoma proteins (Table 2). The JH1 segment is found less frequently and, even then, only in association with a member of the most 5 D family (D-FL16). Thus, most DJH1 joints (with the obvious exception of D-FL16/JH1 -see above) may have been replaced by another DJH complex before VH to DJH joining occurs. 

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