Response to TIA is IgM, no memory cells, no class switch. TIA-2 do not induce Ab production. TDA require TH cells to activate B cells. TH cells are important for the generation of memory cells, affinity maturation of Abs, switch to another class or subclass. Src and Syk and activate them.
Activated kinases phosphorylate tyrosine residues on Ig a and b .
CD19 is then phosphorylated and binds another PTK, Lyn. The final products of the transduction pathways are activated transcriptional factors which migrate to the nucleus and bind to various gene promoters. TH cells provide the second competence signal and the progression signals . B and TH cells form conjugates through TCR on T cells and Ag peptide-MHC II on B cells. CD40L is induced on T cells, and binds to CD40 on B cells.