In article <33E76C67.7F6 at hkstar.com>, Chui Yiu Loon <chuiyl at hkstar.com> wrote:
>One of the central dogmas of immunology is that T cells get stimulated
>by APC in one of those draining lymph nodes, and then they go out to
>look for infected cellular targets and kill them. The infected target on
>their part help those T cells to come to them by secreting some
>cytokines, such as interferon, and expressing adhesion molecules. It is
>all very fine in this way. However, my question is that how does a cell
>know that it is actually infected. This question, as I see it, is very
>important.
There are several ways that a cell "knows" that it is infected. First, they
rely on the fact that viruses frequently transcribe from both strands of DNA
(a result of the need to keep the genome small). Since there will be
complementary RNA sequences generated, some will bind to form double-stranded
RNA, which activates the NF-KB pathway (among others). Another virus-specific
signal is single-stranded DNA, which is an intermediate in the life cycle of
RNA viruses (I believe there are also some ssDNA viruses), and this also
activates cellular signalling pathways. Cells may also be able to detect the
effects of a virus on transcription machinery and metabolic requirements.
Ken Frauwirth
--
Ken Frauwirth (MiSTie #33025) _ _
frauwirt at mendel.berkeley.edu |_) * |/ (_ |\ |
http://www.ocf.berkeley.edu/~frauwirt/ |_) | () |\ (_ | \|
DNRC Title: Chairman of Joint Commission on In-duh-vidual Affairs
