Contribution of the CD5+ B cell to D-proximal VH family expression early in ontogeny

In this study, the contribution of the CD5+ B cell to the preferential expression of VH 7183 and Q52 observed early in development was determined. CD5+ and CD5- B cells from BALB/c mice were isolated by fluorescence-activated cell sorter and the expression of particular VH gene families was determined directly by in situ hybridization. The results indicate that CD5+ B cells obtained from both adult and neonatal animals express Q52 at increased levels compared with CD5- B cells. Preferential expression of VH 7183 was observed only in the neonatal CD5- B cell subset. Thus, the increased expression of VH 7183 early in development is caused by the CD5- subset whereas increased Q52 expression is caused by the CD5+ subset. These results indicate that the fetal/neonatal conventional B cell is distinct from conventional adult B cells in terms of Ig gene repertoire expression.