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  • Title: Ig mu-epsilon isotype switch in IL-4-treated human B lymphoblastoid cells. Evidence for a sequential switch.
    Author: Mills FC, Thyphronitis G, Finkelman FD, Max EE.
    Journal: J Immunol; 1992 Aug 01; 149(3):1075-85. PubMed ID: 1321850.
    Abstract:
    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.
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