In their setting, the co-injection of

LPS did not boost Ab production and the fact that the humoral response had undergone isotype switching was taken as evidence of CD4+ T-cell priming, which was confirmed by using T-cell-deficient mice. When targeting small amounts of antigen to DNGR-1 in the absence of adjuvant, we are unable to induce immunity as assessed by antigen-specific Th1, Th2 or Th17 differentiation or an anti-rat IgG response. Instead, we found that antigen targeting to DNGR-1 in the steady state, if anything, leads to Foxp3+ T-cell differentiation. see more This observation is consistent with the fact that our anti-DNGR-1 antibodies, like those of Caminschi et al., are unable to trigger detectable phenotypic or functional maturation of CD8α+ DC, thought to be a prerequisite for immunity 4, 9, 17. With our reagents, AZD4547 inducing an anti-rat IgG response in the absence of adjuvant was only possible when high amounts of antigen were injected. But even when pushing the system in that manner,

the response remained 2–3 orders of magnitude lower than the one induced in the presence of poly I:C. These data suggest that antigen targeting to DNGR-1 in the absence of adjuvant might lead to Ab production in certain conditions but that the process is inefficient and that DC activation by a potent adjuvant remains important for triggering of a strong humoral response. Thus, our data largely agree with those of Caminschi et al. and any differences might be quantitative and reflect the use of distinct targeting antibodies, possibly bearing different affinities for DNGR-1. The major difference between the two studies is the fact that Caminschi et al. found that the inclusion of adjuvant did not substantially boost Ab titers, whereas in our case, we see a massive increase. This discrepancy might be explained by the fact that Caminschi et al. used PAK6 LPS, which is a poor adjuvant in

comparison with poly I:C for antigen targeting approaches in which CD8α+ DC are the dominant APC (data not shown and 23). It has recently been proposed that human blood lineage-negative HLA-DR+ BDCA-3+ cells may encompass functional equivalents of mouse CD8α+ DC in mice 19. A genome-wide analysis of the transcriptome of different populations of mouse and human leukocytes supports this contention 41. If BDCA-3+ DC prove to have similar properties to the mouse CD8α+ DC population, those cells could become attractive targets for immune manipulation. In mice, targeting to DEC205 has been considered as the “canonical” way to direct antigens to CD8α+ DC. However, there is no evidence that this lectin is expressed on BDCA-3+ DC and additionally human DEC205 has been detected on a large spectrum of hematopoietic cells 3.