Ig mu-epsilon isotype switch in IL-4-treated human B lymphoblastoid cells. Evidence for a sequential switch.
IgE is produced by B lymphocytes that have undergone a deletional rearrangement of their Ig H chain gene locus, a rearrangement that joins the switch region of the mu gene, S mu, with the corresponding region of the epsilon gene, S epsilon. To examine the resulting composite S mu-S epsilon junctions of human lymphoid cells, we have used a polymerase chain reaction strategy to clone the switch regions of the human myeloma U266 and of two IgE-producing human cell lines generated by treatment of lymphocytes with EBV plus IL-4. The switch junction of one of the EBV lines is a complex rearrangement in which a fragment of S gamma is interposed between S mu and S epsilon. This finding suggested that the switch to epsilon in this human lymphoid cell was preceded by a S mu-S gamma recombination. To determine whether this sequential switch rearrangement represented a unique event or occurred with some regularity in human B cells switching to IgE production, DNA samples from bulk cultures of lymphocytes treated with IL-4 were subjected to polymerase chain reaction amplification of their S mu-S epsilon junctions. When the resulting fragments were examined by Southern blotting, a substantial fraction hybridized to an S gamma probe. This finding suggests that sequential recombination involving S gamma is not rare in the switch to epsilon production in humans. Our polymerase chain reaction strategy should be useful in studying isotype switching at the DNA level.
Mills
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Division of Cytokine Biology, Food and Drug Administration, Bethesda, MD 20892.
Thyphronitis
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Finkelman
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Max
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D001402:B-Lymphocytes / Q000502:physiology*; D001483:Base Sequence; D015139:Blotting, Southern; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D005803:Genes, Immunoglobulin; D005812:Genes, Switch; D004854:Herpesvirus 4, Human; D006801:Humans; D007139:Immunoglobulin epsilon-Chains / Q000235:genetics*; D007148:Immunoglobulin mu-Chains / Q000235:genetics*; D066298:In Vitro Techniques; D015847:Interleukin-4 / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D015183:Restriction Mapping; D013997:Time Factors
D007139:Immunoglobulin epsilon-Chains; D007148:Immunoglobulin mu-Chains; D015847:Interleukin-4