APC'S are present almost everywhere in our bodies. It is higly unlikely that
there will be no encounter between a virus and APC's. In addition there is
recent evidence that class I molecules are able to bind antigen in acidic
compartments just like class II molecules do. Search articles on cross-priming.
Also look at PNAS Vol 96, issue 18, 10326-10331. August 31,1999.
