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From: oliver@unc.UUCP (Bill Oliver)
Newsgroups: sci.bio,sci.med
Subject: Re: AOTW08: Hepatitis B core antigen as a T-cell independent antigen
Message-ID: <429@unc.unc.UUCP>
Date: Wed, 17-Dec-86 19:38:51 EST
Article-I.D.: unc.429
Posted: Wed Dec 17 19:38:51 1986
Date-Received: Thu, 18-Dec-86 21:09:18 EST
References: <740@aecom.UUCP>
Reply-To: oliver@unc.UUCP (Bill Oliver)
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Organization: CS Dept, U. of N. Carolina, Chapel Hill
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Xref: mnetor sci.bio:74 sci.med:403

In article <740@aecom.UUCP> werner@aecom.UUCP (Craig Werner) writes:
>!
>
>Note: if you are like me, you are probably wondering what an
>intracellular antigen like HB core antigen is doing being recognized by
>the immune system in the first place.  Well, the phenomenon is not an
>isolated one, although the lack of a need for Helper T-cells is. Even so,
>it has always really bothered me.  After all, the immune system should
>only be seeing things that are exposed, or should it? Explanations are
>beyond me...
>
>-- 
>			      Craig Werner (MD/PhD '91)

I'm not really sure, but two possible explanations come to mind.

The first is that, like almost all viruses, complete packaging of the virion
is not 100% efficient.  When the host cell dies, it releases both the 
complete, infectious, virions as well as the incomplete parts.  In HBV,
of course, the envelope is produced (if my memory serves me right -- I don't
have my references handy) in excess as spherules, which can be detected 
in the circulation in active disease.  This excess of envelope would
argue for high efficiency of covering up the core....

Leading to the second possiblity -- that the circulating complete
virion has the envelope removed by a circulating factor.  In the lab,
you need some sort of detergent to rip off the envelope, but there  
is no reason that it con't be done somewhere by the body. 

I'd be willing to bet that incomplete packaging leads to dumping of
the core, and that a circulating factor, probably immune mediated,
breaks up the core, releasing the e antigen.  While no c is ususally found
in the bloodstream, e antigen is found in acute illness and is an
integral part of the core -- suggesting that perhaps the core was
released and then degraded.  This would allow exposure of both
c and e antigens to the immune system even though only the e is
found in circulating blood.


Sound good?


Bill

"People's Pathologist"