The persistence of donor-derived DCs in lymph nodes is impaired in the presence of host Ly49D⁺ NK cells. (A,B) B6 CD8^−/− mice, treated or not with anti-NK1.1 PK136 mAb, were injected with CFSE^low-labeled syngeneic B6 DCs and CFSE^high-labeled allogeneic BALB/c DCs. Draining lymph nodes were harvested at indicated times after immunization and analyzed for the presence of CFSE-labeled cells. Cells were gated on CD11c^pos, MHC II^high, and CFSE^pos cells. (A) Representative CFSE profiles of injected DCs obtained at 48 hours from untreated or PK136-treated mice. (A,B) Numbers in dot plots and histograms indicate the percentages of allogeneic BALB/c CFSE^high cells normalized to control syngeneic B6 CFSE^low cells [(%BALB/c DCs:%B6 DCs) × 100]. (C) B6 CD8^−/− mice were treated, or not, with anti-NK1.1 PK136 mAb or anti-Ly49D 4E5 mAb, and injected as in panel A with a mixture of CFSE^low-B6 DCs and CFSE^high-BALB/c DCs. Forty-eight hours after immunization, the presence of CFSE-positive cells was analyzed in the draining lymph nodes, and the percentage of CFSE^high BALB/c cells among control CFSE^low B6 cells was determined. Data are mean plus or minus SEM of 3 or 4 mice per group. (D) B6 CD8^−/− mice treated, or not, with PK136 were injected with 1 or 2 × 10⁶ CMTMR-labeled BALB/c DCs. Forty-eight hours after immunization, draining lymph nodes were harvested, prepared and stained with anti-B220 and anti-PNAd mAbs (blue). Lymph nodes sections were then analyzed by confocal microscopy, and the numbers of red DCs per lymph node were evaluated. Data are mean plus or minus SEM of 4 lymph nodes per group (2 mice/group). (E,F) B6 CD8^−/− mice were treated or not with PK136 as indicated before immunization with DCs. (E) Mice were immunized with CMTMR-labeled BALB/c DCs (red). Frozen sections of lymph nodes at 48 hours were stained with goat anti-NKp46 antibodies and then donkey anti–goat Alexa488 antibodies. Numbers of NK cells and BALB/c DCs per section were counted. Data are mean plus or minus SEM of 4 to 6 lymph nodes per group. In panel F, mice were injected with CFSE-labeled BALB/c DCs (green) and CMTMR-labeled B6 DCs (red). Draining lymph nodes were removed at indicated times after immunization to evaluate the kinetics of allogeneic DC appearance. Lymph node sections were then stained with anti-B220 and anti-PNAd mAbs (blue). Representative tissue sections from untreated or PK136-treated mouse lymph nodes harvested at 48 hours after injection are depicted. Histograms indicate the percentage of CFSE BALB/c cells among control CMTMR B6 cells. Data are mean plus or minus SEM of individual lymph nodes (2 or 3 mice per group). *P < .05. **P < .01. N.S. indicates not significant. Data are representative of at least 2 or 3 experiments performed.