Figure 2.

Antigen persisting as immune complexes on FDCs are not necessary to maintain CTL memory. Mice deficient for IgM expression (−/−, solid triangles) that cannot produce antibody and control mice (+/+, open triangles) were immunized with 10 μg of recombinant LCMV-GP protein (Upper) or 10 μg of recombinant VSV-N protein (Lower). Eight to 12 weeks later, spleen cells were restimulated in vitro with the relevant peptides and tested 5 days later in a conventional ⁵¹Cr release assay on peptide-pulsed EL-4 cells. Alternatively, LCMV-GP-primed mice were challenged with LCMV (200 pfu), and virus titers were determined in the spleen 5 days later. VSV-N primed mice were challenged i.p. with recombinant vaccinia virus expressing VSV-N (5 × 10⁶ pfu), and virus titers were determined 5 days later in ovaries. The horizontal line indicates the detection limit. One representative experiment of three is shown.