title: Isotype switching in murine pre-B cell lines.
abstract: Isotype switching at the pre-B cell stage was studied by employing A-MuLV-transformed cell lines. Two gamma 2b-producing cell lines that did not have other cytoplasmic heavy chains or light chains were established from A-MuLV-transformed cell lines. One clone (SL2-1-52) arose spontaneously from a non-Ig-producing cell line (SL2-1) during in vitro culture. Another clone (AT11-2-24-6-99) underwent isotype switching from a mu-producing cell line (AT11-2-24-6), which had been derived from another non-Ig-producing line (AT11-2). Southern blot analysis of two gamma 2b-producing clones was performed in comparison to that of their respective parent clones. The results showed that isotype switching can operate at the stage of pre-B cells by a CH gene deletion mechanism without utilizing the switch region. In addition, the possibility is presented that deletion of the intervening CH genes could occur prior to the formation of the functional V region-coding DNA segment. This indicates that the prior expression of mu chains is not obligatory for the expression of other isotypes and that isotype commitment could occur in pre-B cells.
mesh_terms: D000011:Abelson murine leukemia virus; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D002472:Cell Transformation, Viral; D003001:Cloning, Molecular; D004247:DNA / Q000032:analysis; D004262:DNA Restriction Enzymes / Q000378:metabolism; D005786:Gene Expression Regulation; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007147:Immunoglobulin Light Chains / Q000235:genetics*; D007145:Immunoglobulin kappa-Chains / Q000235:genetics; D051379:Mice
chemical_list: D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D007145:Immunoglobulin kappa-Chains; D004247:DNA; D004262:DNA Restriction Enzymes