The process of antibody isotype switching and somatic hypermutation are important in the development of effective humoral responses. However, their understanding of the mechanisms involved in either isotype switching or somatic hypermutation is limited. The investigators have found that H-chain transgenes can undergo both isotype switching and somatic hypermutation. They have also found that a transgene construct can undergo VDJ sequence transfers that resemble gene conversion and correlate with somatic hypermutation. Surprisingly, analyses of both transgene isotype switching and """"""""conversion"""""""" suggest that an elevated level of homologous recombination/gene conversion activity, which may have specificity for Ig gene sequences, is induced in some antigen-activated B cells. Their suggestion that homologous recombination/gene conversion plays a role in interchromosomal transgene isotype switching is based on an assumption that the Sm tandem repeat region is required for class switch recombination.
One aim i n this proposal will test this assumption; the Sm repeats will be deleted from the IgH locus in mice to ascertain Sm involvement in normal H-chain gene class switching.
A second aim i n this proposal will test the percentage of DNA homology require for transgene homologous recombination/gene conversion and the length of the DNA segments that are involved in the recombination/conversion process. The frequency of these events in differentiating B cells, and the phenotypes of the B cells undergoing the process, will also be investigated.
The third aim of the proposal involves studies directed toward their suggestion that the homologous recombination/conversion process is targeted to antibody H-chain gene sequences. Several transgene constructs will be used to explore whether neighboring sequences affect the frequency of recombination/conversion between homologous gene segments. In addition, whether RNA transcription affects the frequency of recombination/conversion will also be investigated. The results from the proposed studies will demonstrate whether recombination/conversion activities are specifically induced in antigen-stimulated mouse B cells and will elucidate some of the important parameters that govern these processes. They believe that characterizations of these activities may lead to new insights into the poorly understood mechanisms of switch recombination and somatic hypermutation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI024465-13
Application #
2886540
Study Section
Special Emphasis Panel (ZRG2-SSS-4 (02))
Program Officer
Kerr, Lawrence D
Project Start
1987-04-01
Project End
2001-06-30
Budget Start
1999-07-01
Budget End
2000-06-30
Support Year
13
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Tufts University
Department
Pathology
Type
Schools of Medicine
DUNS #
604483045
City
Boston
State
MA
Country
United States
Zip Code
02111
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Shansab, Maryam; Selsing, Erik (2011) p21 is dispensable for AID-mediated class switch recombination and mutagenesis of immunoglobulin genes during somatic hypermutation. Mol Immunol 48:973-8
Eccleston, Jennifer; Yan, Catherine; Yuan, Karen et al. (2011) Mismatch repair proteins MSH2, MLH1, and EXO1 are important for class-switch recombination events occurring in B cells that lack nonhomologous end joining. J Immunol 186:2336-43
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Han, Jin-Hwan; Akira, Shizuo; Calame, Kathryn et al. (2007) Class switch recombination and somatic hypermutation in early mouse B cells are mediated by B cell and Toll-like receptors. Immunity 27:64-75
Wuerffel, Robert; Wang, Lili; Grigera, Fernando et al. (2007) S-S synapsis during class switch recombination is promoted by distantly located transcriptional elements and activation-induced deaminase. Immunity 27:711-22
Selsing, Erik (2006) Ig class switching: targeting the recombinational mechanism. Curr Opin Immunol 18:249-54
Min, Irene M; Rothlein, Lisa R; Schrader, Carol E et al. (2005) Shifts in targeting of class switch recombination sites in mice that lack mu switch region tandem repeats or Msh2. J Exp Med 201:1885-90

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