The document discusses key aspects of the immune response, including the kinetics and qualitative changes that occur during primary and secondary antibody responses. Specifically, it notes that antigens are cleared more rapidly during secondary responses due to memory cells. It also describes how antibody class, affinity, and avidity increase from primary to secondary responses due to somatic hypermutation and affinity maturation of B cells. Finally, it summarizes the cellular events involved in primary versus secondary responses to T-dependent antigens.

1. Ab formation

2. Hallmarks of the Immune Response Self/Non-self Discrimination Memory Specificity

3. Fate of the Immunogen Clearance after 1 o exposure Equilibrium phase Catabolic decay phase Immune elimination phase Clearance after 2 o exposure More rapid onset of immune elimination phase Immune Elimination Phase Days after Injection 2 4 6 8 12 10 Amount of Circulating Ag (%) 25 75 100 50 Equilibrium Phase Catabolic Decay Phase

4. Kinetics of the Ab Response T-dependent Ag; 1 o Response Lag phase Log phase Plateau phase Decline phase Ag D a y s A f t e r I m m u n i z a t i o n A b T i t e r LAG LOG DECLINE PLATEAU

5. Kinetics of the Ab Response T-dependent Ag; 2 o Response * Specificity Lag phase Log phase Plateau phase Decline phase 1 o Ag 2 o Ag D a y s A f t e r I m m u n i z a t i o n A b T i t e r

6. Qualitative Ab Changes during 1 o and 2 o Responses Class variation 1 o - IgM 2 o - IgG, IgA or IgE 1 o Ag 2 o Ag Total Ab IgM Ab IgG Ab D a y s A f t e r I m m u n i z a t i o n A b T i t e r

7. Qualitative Ab Changes during 1 o and 2 o Responses Class variation Affinity Affinity Maturation 1 o Ag D a y s A f t e r I m m u n i z a t i o n A f f I n I t y 2 o Ag IgG Ab IgM Ab High Dose Low Dose

8. Qualitative Ab Changes during 1 o and 2 o Responses Class variation Affinity Clonal selection Somatic mutation 10 10 10 8 10 6 10 5 10 9 10 7 High Ag Concentration 10 10 10 8 10 6 10 5 10 9 10 7 Low Ag Concentration Moderate Affinity Ab High Affinity Ab

9. Qualitative Ab Changes during 1 o and 2 o Responses Class variation Affinity Avidity Cross reactivity

10. Cellular Events in 1 o Response to T-dependent Ags Lag Clonal selection Log IgM Class switching Stationary Decline Memory Cell Pool IgM Memory Cells IgG 1 o Ag

11. Cellular Events in 2 o Response to T-dependent Ags Lag phase Virgin cells Memory cells Log phase Pool size IgG, IgA or IgE Stationary Decline Sustained production IgM Memory Cells IgG IgG Memory Cells Memory Pool Virgin B cell

12. Memory T cells T Cells Virgin cells Memory cells Th cells Cytokines Long Term Memory Th Memory Cells Th Th Memory Cells Memory Pool Virgin cell

13. Kinetics of Ab Response to T-independent Ags 4 Phases IgM antibody No secondary response 1 o Ag 2 o Ag D a y s A f t e r I m m u n i z a t i o n A b T i t e r IgM Ab

14. Class Switching DNA rearrangement Antigen dependent Switch site Same VDJ T H cytokines   L    3   2  1  4  1  2 P L V D J S S S S S S S S P L S   1  2 S S  Primary Transcript IgM or IgD Primary Transcript IgE RNA DNA DNA DNA Rearrangement L V D J V D J V D J

15. Membrane vs Secreted Ig Differential pre-mRNA processing Membrane exons Alternate polyA sites Same VDJ region used mRNA Primary Transcript H3 H4 M M H3 H4 M M AAAA Membrane Bound H3 H4 AAAA Secreted H3 H4 AAAA H3 H4 M M AAAA DNA Polyadenylation Sites