Unusual patterns of immunoglobulin gene rearrangement and expression during human B cell ontogeny: human B cells can simultaneously express cell surface kappa and lambda light chains.
Immunoglobulin gene rearrangement during mammalian B cell development generally follows an ordered progression, beginning with heavy (H) chain genes and proceeding through kappa and lambda light (L) chain genes. To determine whether the predicted kappa-->lambda hierarchy was occurring in vitro, we generated Epstein-Barr virus-transformed cell lines from cultures undergoing human pre-B cell differentiation. A total of 143 cell lines were established. 24 expressed cell surface mu/lambda by flow cytometry and were clonal by Southern blotting. Surprisingly, two of the mu/lambda-expressing cell lines contained both kappa alleles in germline configuration, and synthesis/expression of conventional lambda L chains was directly proven by immunoprecipitation/sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in one of them. Thus, human fetal bone marrow B lineage cells harbor the capacity to make functional lambda L chain gene rearrangements without rearranging or deleting either kappa allele. A third unusual cell line, designated 30.30, was observed to coexpress cell surface kappa and lambda L chains associated with mu H chains. The 30.30 cell line had a diploid karyotype, a single H chain rearrangement, both kappa alleles rearranged, and a single lambda rearrangement. Immunoprecipitation/SDS-PAGE confirmed that 30.30 cells synthesized and expressed kappa and lambda L chains. Multiparameter flow cytometry was used to demonstrate the existence of kappa+/lambda+ cells in fetal bone marrow and fetal spleen at frequencies of 2-3% of the total surface Ig+ B cell population. The flow cytometry data was confirmed by two-color immunofluorescence microscopy. The existence of normal human B cells expressing cell surface kappa and lambda refutes the widely accepted concept that expression of a single L chain isotype is immutable. The kappa+/lambda+ cells may represent transients undergoing L chain isotype switching.
Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis 55455.
M E
ME
Pauza
J A
JA
Rehmann
T W
TW
LeBien
D001402:B-Lymphocytes / Q000276:immunology*; D002454:Cell Differentiation; D002461:Cell Line, Transformed; D005260:Female; D015321:Gene Rearrangement; D005803:Genes, Immunoglobulin; D006412:Hematopoietic Stem Cells / Q000276:immunology*; D004854:Herpesvirus 4, Human / Q000235:genetics; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000032:analysis* / Q000235:genetics; D007146:Immunoglobulin lambda-Chains / Q000032:analysis* / Q000235:genetics; D011247:Pregnancy; D011947:Receptors, Antigen, B-Cell / Q000032:analysis*
D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D011947:Receptors, Antigen, B-Cell