I believe what the first author (Ralph) may be thinking of is the
so-called "original antigenic sin." If you immunize with an antigen,
let's called it HA-1, and later immunize with an antigen that differs
from the first by only one amino acid (HA-2), you sometimes find
that Ab titers against the new epitope on HA-2 are lower than if you
had just immunized with HA-2 alone. In fact, antibody titers against
the first epitope can rise after the boost, even though that epitope was
not present in the HA-2 boost. (Cross-reactivity)
But that's not always the case. Sometimes titers against both epitopes
suffer. The immune response typically focuses on only a few epitopes
per antigen even though it has the capacity to respond to more. (This
is most pronounced for T-cell epitopes, but is also true for B-cells).
If one of these favored epitopes is altered, it sometimes loses this
favored status, so to speak.
That said, I'm pretty sure that original antigenic sin is not generally a
serious concern. It's better to be vaccinated than not.
Paul Olson
-----
Justin Cobb writes:
------
| If the slightly different strain is so similar to the original strain
that
| the immune system would react as though it has seen it before, the same
| antibodies would probably bind to the slightly different virus just as
it
| would to the original. When the immune system produces B-cells specific
to
| a specific antigen, they will remain for a fairly long time. If the
body is
| invaded by an antigen that fits in the same antigen-binding site later
on
| whether it is the same antigen or one that is very similar, the B-cells
will
| produce antibodies as soon as they "detect" the antigen. This is known
as
| immune "memory." Immune memory will not be activated (i.e., the antigen
| will not be recognized as something that the immune system has "seen"
| before) if the antigen does not bind to the receptors on a B-cell (I
think
| they are called membrane-bound antibodies, but I'm not certain.)
because the
| B-cell for a specific antigen is not produced until that antigen is
| introduced to the body.
||-
| Justin Cobb
| Sophomore, Biology-General
| University of Illinois at Urbana-Champaign
| School of Life Sciences
RSAMSON18 at cs.com> wrote in message news:13.4aafaff.263fb59c at cs.com...
> What I was suggesting in my original posting is if one is vaccinated
for
one
> of the
> Type A strain of virus and what comes along is a very slightly
different
> strain of the
> Type A virus, the immune system may think "I've seen this before" and
not
try
> to
> produce new antibodies until too late. This may only happen rarely and
only
> with the
> devilish flu virus. I still consider it a possibility mainly based on
the
> results, which
> was that the outbreak was much more severe on a very high percentage of
those
> were vaccinated.
> Ralph L. Samson
> ---
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