For instance, IL-7 is essential for the generation of murine pre-B cells and the IL-7 receptor synergizes with the pre-BCR to activate pre-B cell cycling 28, 29. This dual regulation of early B-cell generation might be important to prevent an uncontrolled proliferation of pre-B or

autoreactive B cells, while allowing a certain magnitude of cell cycling, which is followed by the rearrangement Poziotinib in vivo of the LC genes. Thus, regulating the concentration of growth factors in the microenvironment or altering the responsiveness of developing B cells to these factors seems to control the switch from proliferation to differentiation (i.e. LC gene rearrangement) in response to pre-BCR or autoreactive BCR signaling. Conversely, combining autoreactive BCRs with elevated expression of growth factors

such as IL-7 might lead to lymphoproliferative and/or autoimmune diseases as suggested by transgenic over-expression of IL-7 30. It would be interesting to test whether the BCRs of these immature B-cell lymphomas possess increased autoreactivity and whether selleck this is involved in the increased lymphoproliferation. Altogether, understanding the positive role of autoreactivity in precursor B-cell proliferation not only highlights the importance of pre-BCR expression for early B-cell selection but might also help to explain the molecular mechanisms that underlie the development of autoimmune and lymphoproliferative diseases. Our study demonstrates the importance of autoreactivity for proper B-cell development with the pre-BCR

being an invariantly autoreactive Fossariinae receptor. In the presence of a strongly recognized antigen the self-reactivity of the pre-BCR can be substituted by an autoreactive BCR to allow efficient generation of B cells. Thus, it is conceivable that at the early immature B-cell stage, cells bearing an autoreactive BCR may continue to proliferate and to recombine their LCs just as their pre-B cell predecessors do. After having changed their autoreactive specificity by receptor editing, such BCRs may get stably expressed on the surface of immature B cells, which then proceed in development. Our results are reminiscent of a hypothesis published by Niels Jerne in the very first issue of this journal 40 years ago, in which he proposed the selection of escape mutants through the initial expansion and subsequent negative selection of progenitor cells expressing germ line encoded autoreactive receptors as a mechanism of somatic antibody diversification 31. Mb1-lox-GFP mice 18, λ5−/− mice 10, 3-83Igi mice carrying the pre-rearranged 3-83Hi/33-83κi Ig gene segments 14 and mice carrying the B1-8Hi/3-83κi Ig gene segments 15 were used in this study. All mice used for the generation of HSCs were backcrossed on H-2d background. Rag-2/λC−/− mice 17, either on Balb/C or BL/6 background, were used as recipient mice for adoptive transfer experiments.