Cross‐priming of CD8+ T cells by viral and tumor antigens is a robust phenomenon

Abstract

"Cross‐priming" refers to the activation of naive CD8⁺ T cells by antigen‐presenting cells that have acquired nominal antigens from another cell. The biological relevance of cross‐priming of CD8⁺ T cells has recently been challenged (Zinkernagel, R. M., Eur. J. Immunol. 2002. 32: 2385–2392), on the basis that responses are weak or poorly quantitated, and the determinants recognized are undefined. Here we show that cross‐priming is a robust process that elicits vigorous primary responses to multiple peptides in two well‐defined systems. Our findings support the relevance of cross‐priming in CD8⁺ T cell responses to viruses and tumor cells, and demonstrate that cross‐priming elicits CD8⁺ T cells to determinants generated by the endogenous processing pathway.