high slope (b-value) of standard curve - (Jul/05/2013 )

So I am presuming that you wish to estimate the quantity of antibodies specific to your protein x, which is either a pathogen/ vaccine / biological therapeutic. Each individual will mount an immune response to protein X in his/her own individual way so the antibodies from each individual will bind to protein X with varying affinity/avidity, so your results will always be relative to whatever standard you adopt and not truly quantitative.

It may be possible to affinity purify specific antibodies from positive serum samples using a protein X affinity matrix followed by acid elution of the specific antibodies and quantify the eluted antibodies and create a standard curve from that. You could use this as your own reference which you will always refer back to. Alternatively, you could generate a polyclonal anti protein X antibody in a different species (and this may be acceptable in certain disciplines but your detection antibody would have to cross react with human and poly species IgG) or generate an engineered human mAb or panel of human mAbs specific for protein x. Several providers can do this for you, one you might look into is HuCal antibodies from Abd Serotec if funds permit.

With that said, there are published guidelines for immunogenicity testing of therapeutics/vaccines etc, which take into consideration many factors including antigen tolerance (your assay won't work if you have antigen X in the sample binding to the anti-antigen X antibodies). Relevant guidelines for anti-therapeutic antibodies can be found by googling 'Immunogenicity testing guidelines - Millipore', I am sure you can find similar guidelines for vaccines/pathogens/or other...time spent becoming familiar with the specific approaches for your particular discipline would be very useful before moving forward.

I think all here are agreed that the human IgG quantification kit is not helpful in this endeavour.

good luck

Thank you, yes, your paragraph 1 statement is what we are trying to accomplish, only a relative measurement, not really quantitative. I will bring your comments up with the scientist to re-think our approach.