Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rutgers!ames!ucbcad!ucbvax!decvax!linus!philabs!aecom!werner From: werner@aecom.UUCP (Craig Werner) Newsgroups: sci.bio,sci.med Subject: AOTW08: Hepatitis B core antigen as a T-cell independent antigen Message-ID: <740@aecom.UUCP> Date: Tue, 16-Dec-86 00:52:29 EST Article-I.D.: aecom.740 Posted: Tue Dec 16 00:52:29 1986 Date-Received: Thu, 18-Dec-86 00:30:16 EST Organization: Albert Einstein Coll. of Med., NY Lines: 42 Keywords: Science 234:1398 (12 Dec 1986) Xref: mnetor sci.bio:68 sci.med:397 ! [Abstract of the Week, AOTW, is a weekly (more or less) feature of sci.bio] ! The Nucleocapsid of Hepatitis B Virus is Both a T-Cell-Independent ! and a T-Cell-Dependent Antigen. ! Milich DR and McLachlan A ! Science 234:1398 (12 Dec 1986) One characteristic of the immune response during hepatitis B virus (HBV) infection in humans is the vigorous production of antibodies of immunogloulins (Ig) M and G to nucleocapsid antigen (HBcAg). In this study HBcAg was shown to be similarly immunogenic in mice. When injected into athymic (nude) B10.BR and athymic BALB/c mice, HBcAg induced IgM and IgG class antibodies in spite of the absence of T cells in nude mice. In euthymic mice, HBcAg efficiently stimulated T-cell proliferation in vitro and helper T-cell function in-vivo. The dual functions of HBcAg as a T-cell independent and a T-cell dependent antigen may explain its enhanced immunogenicity. Denaturation of HBcAg yields a nonparticulate antigen designated HBeAg; when HBeAg was used as the immunogen, antibody production required helper T-cell function. Although HBcAg and HBeAg are serologically distinct, they are structurally related, and in these experiments were highly cross-reactive at the T-cell level. These results suggest that the elevated levels of IgM antibodies to HBc and the enhanced immunogenicity of HBcAg during HBV infection in humans reflrect the ability of HBcAg to directly activate B cells to produce antibodies to HBc in the presence or absence of HBcAg- or HBeAg-sensitized T-cells. 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) !philabs!aecom!werner (1935-14E Eastchester Rd., Bronx NY 10461, 212-931-2517) "It's hard to argue with someone who knows what he's talking about."