Immature surface Ig+ B cells can continue to rearrange kappa and lambda L chain gene loci.
Pro and pre B cells possess the long-term capacity to proliferate in vitro on stromal cells and interleukin 7 (IL-7) and can differentiate to surface immunoglobulin (sIg+) cells upon removal of IL-7 from the cultures. A key event in this differentiation is the extensive cell loss due to apoptosis. Because the proto-oncogene bcl-2 can promote cell survival, we established pre-B cell lines from E mu-bcl-2 transgenic mice. These pre-B cells have the same properties as those derived from non-bcl-2 transgenic mice except that they do not die by apoptosis. This allowed us to study the fate of newly formed B cells in vitro for a longer period of time. Here we show that early during the differentiation of pre-B cells, upregulation of RAG-1 and RAG-2 expression go hand in hand with rearrangements of the Ig gene loci. Moreover, the newly formed sIg+ B cells continue to express RAG-1 and RAG-2 and continue to rearrange L chain gene loci, even in the absence of proliferation, in an orderly fashion, so that kappa L+ sIg+ cells can become lambda L+ sIg+ or sIg- cells, whereas lambda L+ sIg+ cells can become sIg-, but not kappa L+ sIg+ cells. Thus, deposition of a complete Ig molecule on the surface of a B cell does not automatically stop the Ig-rearrangement machinery.
Basel Institute for Immunology, Switzerland.
A
A
Rolink
U
U
Grawunder
D
D
Haasner
A
A
Strasser
F
F
Melchers
D000818:Animals; D017209:Apoptosis; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology; D001483:Base Sequence; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D004268:DNA-Binding Proteins; D015328:Gene Rearrangement, B-Lymphocyte, Light Chain; D018398:Homeodomain Proteins; D006918:Hydroxyurea / Q000494:pharmacology; D007145:Immunoglobulin kappa-Chains / Q000235:genetics*; D007146:Immunoglobulin lambda-Chains / Q000235:genetics*; D015851:Interleukin-7 / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D011518:Proto-Oncogene Proteins / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2; D011947:Receptors, Antigen, B-Cell / Q000096:biosynthesis / Q000276:immunology / Q000502:physiology*
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D015851:Interleukin-7; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C499308:Rag2 protein, mouse; D011947:Receptors, Antigen, B-Cell; C064655:V(D)J recombination activating protein 2; C064658:RAG-1 protein; D006918:Hydroxyurea