Ig isotype switching in B lymphocytes. A method for estimating isotype switch frequency in cloned B cell lymphomas.
We have developed a method for enumerating the frequency of Ig isotype switching in clones of B cells. The method adapts Poisson statistics to analyze the distribution of amounts of switched isotype produced by multiple subclones of cells and thus enables one to estimate the probability that a single cell will switch isotype in one cell generation. We have applied this method to determine the spontaneous switch frequency of two Ly-1+ B cell lymphomas of B10-H-2aH-4bp/Wts mice. Both CH12.LX and CH27.LX switch from IgM to IgA at very high frequencies (1 - 5 x 10(-3) switch events per cell division) and from IgM to IgG at low but detectable frequencies (10(-4) - 10(-5) switch events per cell division). Cloned IgG variants of CH12.LX switch to IgA at the same frequency as the IgM-producing cells. Bacterial lipopolysaccharide has a strong inhibitory effect on isotype switching by CH12.LX. Possible explanations for the observed preference for switching to IgA are discussed.
Whitmore
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Department of Microbiology and Immunology, University of North Carolina, Chapel Hill 27599.
Prowse
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Arnold
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Haughton
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D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D002455:Cell Division; D002999:Clone Cells / Q000276:immunology; D007132:Immunoglobulin Isotypes / Q000096:biosynthesis* / Q000235:genetics; D007134:Immunoglobulin Switch Region; D016393:Lymphoma, B-Cell / Q000235:genetics / Q000276:immunology; D014407:Tumor Cells, Cultured / Q000276:immunology
D007132:Immunoglobulin Isotypes