Figure 2. Antibody-mediated control of viral propagation by NK cells.

(A) Experimental scheme. Mice were infected and mAb-treated as in Figure 1A. Infected/treated mice were treated as indicated with the anti-Ly6G 1A8 mAb or the isotype control 2A3 mAb to deplete neutrophils and infected/treated mice were treated as indicated with the anti-asialo-GM1 antibody to deplete NK cells. (B) Effect of neutrophils or NK cell depletion in viral spread in infected/treated mice. Percentage of infected cells at day 14 p.i. in the spleens of naive, I/NT, and I/T mice, depleted or not of neutrophils or NK cells assessed as in Figure 1C. The data represent 3 independent experiments, with at least 8 mice per group. (C and D) In vivo cytolysis activity of 667 mAb in naive mice after depletion of neutrophils or NK cells. Splenocytes from noninfected mice (Sp) were labeled using 0.5 μM of the vital dye CFSE (CFSE^lo cells; M1) and mixed at a 1:1 ratio with splenocytes from infected mice (Infected-Sp) labeled using 5 μM CFSE (CFSE^hi cells; M2) and preincubated, or not, with 667 mAb. Mixed cell populations were administered to naive mice 1 day after depletion of either neutrophils or NK cells with the 1A8 mAb or the anti-asialo-GM1 antibody, respectively. Cytolysis was quantified 5 hours later, as described in Methods section. The data are presented as mean ± SEM of 2 independent experiments, with at least 8 mice per group. Statistical significance was established using a parametric 1-way ANOVA test with a Bonferroni correction (B and D). (E) Effect of NK cell depletion in the survival of infected/treated mice. I/T, NK cells, depleted or not as indicated in A, were followed up for leukemic death. The data represent 2 independent experiments, with 7 mice per group. Statistical significance was established using an unpaired Student’s t test. Data are expressed as mean ± SEM (*P < 0.05, **P < 0.01,***P < 0.001).