Immunsing to get IgG

[Chris Weir]

Hi all,
   I was just wondering if anyone knew of any good papers on theories 
why when immunising with specific organisms or proteins the IgM 
response dominates even after a full immunisation programme.
 I've got one theory that some antigens (due to there 
characteristics ie too large etc.) when introduced do not require the 
help of T-Lymphocytes to stimulate B-Cells into antibody production . 
Resulting in less isotype switching and reduced affinity maturation 
of mabs produced.
 Does anyone know any more theories?

Thanks in Advance

Chris Weir
Macquarie University