The induction of virus-specific CTL as a function of increasing epitope expression: Responses rise steadily until excessively high levels of epitope are attained

The role of epitope expression levels in CD8(+) T cell priming has been con troversial. Yet this parameter is of great importance in the design of rati onal approaches to optimize CTL responses to a variety of pathogens. In thi s paper we examine the influence of epitope production on CD8(+) T cell pri ming by exploiting a system that allows a 200-fold range of cell surface ep itope expression in vitro with a fixed dose of vaccinia virus. Our results demonstrate that, with the exception of a notable decline at the highest le vel of epitope, the magnitude of the responding CTL population generated in vivo following equivalent viral infections is essentially proportional to epitope density.