Prime Killers

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Science  10 Nov 2000:
Vol. 290, Issue 5494, pp. 1053
DOI: 10.1126/science.290.5494.1053b

Cells infected with viruses and intracellular bacteria trigger their own destruction by presenting antigenic fragments of the pathogen to cytotoxic T cells (CTL). Preceding this is a crucial priming phase in which naive T cells develop their killer phenotype through stimulation by “professional” bone marrow-derived antigen presenting cells (APC) that have acquired antigenic polypeptides from the pathogen.

In exploring the role of APC in CTL priming, Lenz et al. and Sigal and Rock observed that one particular epitope from mouse LCMV virus induced CTL, even when the appropriate bone marrow-derived APC were almost completely absent. For Lenz et al. this finding indicates that cells other than professional APC could participate in the priming of some anti-viral CTL. Sigal and Rock, on the other hand, argue that because of the vigorous replication of this virus, more antigen could be presented by a small number of remaining APC. They also observed that APC could prime a limited CTL response to another epitope of LCMV in the absence of the molecular transporter TAP, which is normally required for antigen processing, suggesting that this relatively inefficient pathway of CTL priming may operate when there is a high viral load. — SJS

J. Exp. Med.192, 1135 (2000); J. Exp. Med.192, 1143 (2000).

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