Boosting protein immunisation lowers Ab response

Mike Clark mrc7 at
Fri Mar 3 06:26:59 EST 2000

In article <unknown-0203001206430001 at>, Shared Mac
<URL:mailto:unknown at> wrote:
> Hello to the denizens of bionet.immunology - I have a quick question.
> Does anyone know if there are examples in the literature similar to the
> following observation?
> Following primary immunisation with a protein antigen (delivered using a
> novel adjuvant) IgG Ab responses were observed that were significantly
> higher than the response to Ag delivered in buffer.
> Following a boost immunisation responses with adjuvant were even higher.
> Following a second boost immunisation IgG Ab responses in the groups
> receiving Ag in adjuvant had decreased compared to post-first boost and
> were then not significantly different from the response in the groups
> receving Ag in buffer.
> Responses in the groups receiving buffer increased post-second boost so
> this effect is not due to some problem with the Ag used in the second
> boost.
> Immunisations were s/c in mice.
> Note also that at a low Ag dose Ab responses increased post-primary,
> post-first boost and post-second boost for Ag delivered in adjuvant and
> buffer.
> Thanks for any pointers - please reply to the group.

You don't give details of timing or of the assay used for Ig. I can think
of two things that you should check for. 

[1] One is that you might be forcing the immune reponse to class switch to
a class or sub-class whihc you are not detecting in your assays.

[2] You might be forcing the system into a state of tolerance or
suppression for antibody responses to your antigen. This is more likely
with higher doses of antigen given more frequently.

Mike                            <URL:>
 o/ \\    //            ||  ,_ o   M.R. Clark, PhD. Division of Immunology
<\__,\\  //   __o       || /  /\,  Cambridge University, Dept. Pathology
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