Downloaded from: StudentConsult (on 26 October 2008 11:36 AM) © 2005 Elsevier Molecular mechanisms of heavy chain isotype switching. In the absence of helper T cell signals, B cells produce IgM. When antigen-activated B cells encounter helper T cell signals (CD40L and, in this example, IL-4), the B cells undergo switching to other Ig isotypes (in this example, IgE). These stimuli initiate germline transcription through the Iε- Sε-Cε locus. The proximal CH genes are deleted in a circle of DNA, leading to recombination of the VDJ complex with the Cε gene. Switch regions are indicated by circles labeled Sμ or Sγ. Iγ represents an initiation site for germline transcription. (Note that there are multiple Cγ genes located between Cδ and Cε, but these are not shown.)
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Downloaded from: StudentConsult (on 26 October 2008 11:36 AM)© 2005 Elsevier
Molecular mechanisms of heavy chain isotype switching. In the absence of helper T cell signals, B cells produce IgM. When antigen-activated B cells encounter helper T cell signals (CD40L and, in this example, IL-4), the B cells undergo switching to other Ig isotypes (in this example, IgE). These stimuli initiate germline transcription through the Iε-Sε-Cε locus. The proximal CH genes are deleted in a circle of DNA, leading to recombination of the VDJ complex with the Cε gene. Switch regions are indicated by circles labeled Sµ or Sγ. Iγ represents an initiation site for germlinetranscription. (Note that there are multiple Cγ genes located between Cδ and Cε, but these are not shown.)
Downloaded from: StudentConsult (on 26 October 2008 11:36 AM)© 2005 Elsevier
Downloaded from: StudentConsult (on 26 October 2008 11:36 AM)© 2005 Elsevier
Downloaded from: StudentConsult (on 26 October 2008 11:36 AM)© 2005 Elsevier
Downloaded from: StudentConsult (on 26 October 2008 11:36 AM)© 2005 Elsevier
Downloaded from: StudentConsult (on 26 October 2008 11:36 AM)© 2005 Elsevier
Downloaded from: StudentConsult (on 26 October 2008 11:36 AM)© 2005 Elsevier
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