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. If the infected cell itself does not alarm the immune system
by releasing such distress signal as cytokines, simply by presenting the
foreign epitopes with its MHC class I molecules cannot be very useful,
as T cells and other phagocytic cells won't be able to find their way
there. If a virus is smart enough, it should be able to evade immune
attack by quietly and carefully replicating inside the cell without
causing distress and transmitting its progeny to neighbouring cells via
direct cell-cell contact. How successful is that strategy will in the
end have to hang on to how sensitive is the host cell in detecting
abnormality inside itself. Therefore, the crucial question remains: how
does a cell start to know it has got an infection?
I shall appreciate it very much if anyone can throw some light on this.
Yiu-Loon Chui
Chinese University of Hong Kong
