Andreas Ehlich

Immunoglobulin heavy and light chain genes rearrange independently at early stages of B cell development

The compartment of mouse B cell progenitors can be resolved into five developmentally related fractions by multicolor flow cytometry. Using this system and employing mutant mice in which the membrane exon of the mu chain, the lambda 5 gene, or the JH locus was inactivated by gene targeting, we found that expression of the pre-B cell receptor complex is necessary for the transition from the large CD43+ to the small CD43- pre-B cell stage. We report the occurrence of immunoglobulin heavy and light chain gene rearrangement at the stage of large B cell precursors. We show that neither the pre-B cell receptor complex nor any gene rearrangement in the heavy chain locus is required for the induction of kappa light chain gene rearrangement in early B cell progenitors.

Early B‐Cell Development in the Mouse: Insights from Mutations Introduced by Gene Targeting

Whether a cell committed to the B-cell lineage finally succeeds in entering the pool of newly-generated B cells depends on the Ig gene rearrangements it acquires during its differentiation. During the past decade, the immunoglobulin (Ig) gene rearrangement program has heen analyzed with the help of Abelson virus-transformed pre-B cell lines that spontaneously undergo rearrangement of Ig loci in vitro. Based on these studies, the following mode! of B-cell development was formulated (Alt et al. 1984, 1987): B-cell precursors first assemble D^JH rearrangements. As soon as a productive VH-*DHJH joint is made, IgH rearrangement ceases and L (light) chain loci are rearranged. For IgL gene rearrangement again an order has been postulated: V Ĵ̂ . joints were suggested to be generated prior to V^J; joints. Once a L chain is expressed, the cell displays surface immunoglobulin (sig) and further Ig gene rearrangements are stopped. We have used gene-targeted mice to analyze the in vivo requirements for B-cell differentiation. While B-cell development in mice lacking membrane-bound /j.-

Analysis of immunoglobulin gene rearrangements in single B cells.

The polymerase chain reaction allows the characterization of RNA and DNA sequences in samples as small as a single cell. The recent development of amplification systems designed to isolate rearranged immunoglobulin genes from single B lineage cells has provided a powerful tool to investigate various aspects of B-cell development.

Discrimination of monozygotic twins (and clones) on the DNA level

Recent DNA typing methods (RFLP, STR, RAPD; e.g., [Naturwissenschaften 84 (1997) 181] [3]) do not allow discrimination of monozygotic twins. To overcome this restriction, we suggest the use of variable DNA sequences of bone-marrow-derived memory B lymphocytes that are likely to be different even in monozygotic twins. Since memory B cells are transported in the blood stream, they can be found in blood stains on crime scenes and checked for a match to the cells of a living twin pair of twins. D 2003 Elsevier Science B.V. All rights reserved.