2. When Do Isotypes Matter? The primary -> secondary immune response: Increase Ig titer Switch from IgM to IgG Increase Ag binding affinity

3. Where and when do affinity maturations and isotype class switch occur?? BCR:mIgM sIgGmIgG CSR/SHM

4. Infection and Ag presentation

9. T cell zone B cell zone Red pulp border Generation of plasmablasts in the spleen

10. T cells: CD4+ and CD8+ CD8+ CD4+

11. APCs: present Ag in the context of MHC class II to T helper cells

12. Ag presentation to T helper cells in the spleen

13. T helper cells are CD4+ are activated by APCare activated by APC secrete cytokines tosecrete cytokines to augment the immune response

14. T helper cells polarize into T H 1 and T H 2 cells into T H 1 and T H 2 cells and secrete unique and secrete unique combinations of combinations ofcytokines

15. Cytokines target germline transcripts to specific Ig isotypes in B cells

16. Cytokines target germline transcripts to specific isotypes 3333 2b  2b

17. T cell zone B cell zone Red pulp border Germinal Center

18. SHM Occurs in the Germinal Center B Cells

20. Primary focus SHM Occurs in Germinal Center B Cells

21. T cell zone Red pulp border Germinal Center Primary focus plasmablasts T cell zone

23. sIgM sIgM and sIgG