Novel insights into class switch recombination

The discovery of activation-induced cytidine deaminase, a putative RNA editing enzyme essential for both class switch recombination and somatic hypermutation, marked the field of isotype switching studies in the year 2000. More recent work from the same group now highlights some essential mechanistic aspects of the switch recombination process. In particular, much has been learnt about the relationship between transcription and recombination and the transcriptional competence of intronic promoters on looped-out circular DNA uncoupled from the proximal and distal enhancers. These findings have far-reaching implications, particularly for studies of class switch recombination in tissues. Although these important advances do not directly relate to interleukin-4-dependent immunoglobulin E switching, the conceptual and experimental tools developed through these studies are certain to foster progress in the immunoglobulin E field.