4. Gene arrangements (human chromosome 22) (human chromosome 2) (human chromosome 14)

5. Tonegawa’s Experiment: Embryo and plasmacytoma DNAs were digested with the restriction endonuclease BamHI, and DNA fragments of different sizes were separated by electrophoresis in agarose gels. The gel was then cut into slices, and DNA extracted from each slice was hybridized with radiolabeled probes that had been prepared from immunoglobulin mRNA isolated from the plasmacytoma cells. Two probes were used, corresponding either to the complete immunoglobulin mRNA or to the 3′ half of the mRNA, consisting only of constant-region sequences. Evidence for Somatic Rearrangement of Immunoglobulin Genes Coding for Variable and Constant Regions. Nobumichi Hozumi and Susumu Tonegawa Basel Institute for Immunology, Basel, SwitzerlandTonegawa Proceedings of the National Academy of Sciences, USA, Volume 73, 1976, pages 3628–3632

6. In embryo DNA, the complete probe hybridized to two BamHI fragments of approximately 8.6 and 5.6 kb, respectively. Only the 8.6-kb fragment hybridized to the 3′ probe, suggesting that the 8.6-kb fragment contained constant-region sequences and the 5.6-kb fragment contained variable-region sequences. In striking contrast, both probes hybridized to only a single 3.4-kb fragment in plasmacytoma DNA. The interpretation of these results was that the variable- and constant-region sequences were separated in embryo DNA but rearranged to form a single immunoglobulin gene during lymphocyte development.

7. Circular DNA isolated from thymocytes undergoing TCR rearrangement (these rearrange just like Ab genes)

8. From Hozumi and Tonegawa, 1976, PNAS USA 73: 3628

11. Kappa gene expression

12. Recombination signal sequences

15. H-gene expression

17. RAG 1 and 2 Recombinase Activating Genes

18. Secreted vs. membrane forms of IgM

20. Class switching by alternative processing

21. Class switching

23. Nucleotide addition during joining When ss DNA is generated:Extra nucleotides can also be added:

24. Secretory pathway

27. Somatic variation

28. Allelic exclusion (only in B and T cells)

29. Model of allelic exclusion

30. cis-acting sites