Selection of VH gene repertoires: differentiating B cells of adult bone marrow mimic fetal development.

In the present study we have compared by in situ hybridization and by a CFU-B colony assay VH family usage in the pre-B and B cell compartments of the bone marrow of adult BALB/c and C57BL/6 mice. We have found that the position dependent increased expression of the VH 7183 family, observed in neonatal mice, is characteristic of early differentiating B cells of adult mice. The quantitative analysis for each VH family of the number of pre-B and B cells produced daily and the number of mature B cells present in the peripheral immunocompetent cell pool of adult BALB/c demonstrates the existence of selecting mechanisms operating within the bone marrow at the level of the emergent repertoire and at the level of export of newly formed cells into the periphery. This selective process results in the decreased peripheral representation of the VH 7183 family and in the accumulation of cells belonging to the other VH families. Selection of VH family usage in peripheral repertoires may be determined according to lymphocyte life-span, as we have found a preferential utilization of the VH J558 family in populations of partially enriched, long-lived B cells.