Ok a few things:
Mike Clark wrote:
>That is possibly a true explanation but the same antibody did not react
>with human brain. I don't know if the levels of CD4 expression are
>different in human and sheep.
>I believe in humans it's very low - you need a very sensitive assay to
detect CD4. This is true of many macrophage markers on microglea - some
people argue that because so many macrophage markers are downregulated
that microglea are not "true" macrophage.
><snip>
>>Included in there is analysis of a paper on antibodies to different species
>of lysozyme in which I point out that "specificity" and "affinity" are not
>easily related concepts.
>I missed one point, although I don't know if this addresses the issue
you bring up. They compare the affinity of the "antibody to the
antigen" vs. the affinity of the antibody to a "random panel of
antigens" (cell lysate I believe). Specificity is measured as having
high affinity for the antigen with low affinity for random - but as I
mentioned earlier this may be specific (no pun intended) to their field.
>Yes but that is also partly because of a process of selection. The
>frequency of B-cells making an antibody of any given specifity might be low
>initially but it can be enhanced through selection and clonal expansion.
>>What of T-independent immune responses, are they not also specific?
>Never claimed they aren't. But AFAIK these antibodies still go through
affinity maturation and thus gain greater affinity compared to the
initial, naive B-cells.
>Look I'll give another example.
>>I inject a mouse with human IgG as an antigen, and get back some
>monoclonals which react with human IgG1, IgG2, IgG3 and IgG4 equally. Other
>monoclonals react only with IgG1 but not with IgG2 3 or 4, and other
>monoclonals react only with the allotype G1m(1,17) but not G1m(3).
>>So which of these monoclonal antibodies do you consider specific and which
>are not specific?
>But in this case it is more likely the multi-reacting antibodies are
identifying shared epitopes between the different sub-classes. For
those antibodies I would say that they are specific to a shared epitope.
Considering the high degree of homology between the different IgG's it
is more then likely that they would be recognizing area's with 100%
protein homology.
><snip>
>>[snip] Must rush now. I'll deal with your other points tomorrow, but the
>Tour de France beckons.........
>>Wouldn't worry about it - I'll probably miss your post as I'm leaving
for a week of SCUBA Friday. Besides, we've gone a long way from the
origonal question (can I make one antibody that recognises 2 distinct
and unrelated proteins). That said, I would recommend the origonal
poster listen to you, as you obviously know more about this then I...
Bryan
