In the murine-Langerin-DTR models, developed originally to target only LCs, it was realized subsequently that both CD207/Langerin+ DDCs and LCs were ablated by diphtheria toxin treatment. Because the two DC
subsets reconstituted CP-690550 cost with different kinetics, interpretation of the effect on T cell responses was complex [63-65]. Finally, depletion of CD205+ DCs in CD205-DTR mice dramatically reduced CD4+ and CD8+ T cell responses to bacterial and viral infections . However, given that the steady-state frequency and distribution of Tregs, Th1 and Th17 cells was grossly altered by diphtheria toxin treatment, it was difficult to attribute the effect solely to CD205+ DCs, without considering the effect of the altered immune environment . CD11c-cre and Langerin-cre mice have also been used to generate targeted knock-outs of multiple immune signalling molecules, including recombination signal binding protein for immunoglobulin kappa J (RBPJ) , signal transducer and activator of transcription 3 (STAT3) , tumour necrosis factor, alpha-induced protein 3 (TNFAIP3) (A20)  and myeloid differentiation primary response gene 88 (Myd88) . These applications suffer from the same subset specificity issues as the DTR models, due to model-dependent artefacts
and the complex expression patterns of Langerin and the CD11c transgene [70, 71]. Administration of horse cytochrome c is an alternate strategy used to ablate cross-presenting DCs via specific induction of the apoptosis pathway in
cells possessing cross-presentation machinery . Experiments using this treatment have suggested that cross-presentation is ICG-001 chemical structure limited to a subset of splenic CD8+ cDCs, although the many model was complicated by the partial depletion of CD11b+(CD4+) cDCs, which are usually considered to be incapable of cross-presentation . In addition to inducible ablation, transcription factor knock-out mice have been used to define in-vivo DC subset function, as they show complete or partial deficiencies in well-defined DC subsets (reviewed in [1, 74]). For example, the comparison of interferon regulatory factor 4 (IRF4–/–) mice (lacking CD11b+ DCs) with Id2–/– or IRF8–/– mice (both lacking CD8+ DCs) has supported the paradigm that CD11b+ DCs promote Th2 cytokine production, while CD8+ cDCs promote Th1 cytokine production [75, 76]. Similarly, basic leucine zipper transcription factor, ATF-like 3 (BATF3–/–) mice have been used to demonstrate that cross-presentation is confined to the CD8+ cDC and CD103+ mDC subsets, which are selectively deficient in these mice . Interestingly, while both CD205-DTR  and BATF3-deficient mice  lack CD8+ cDCs, only in the CD205-DTR model were splenic CD4+ T cell responses affected. An additional complexity in transcription-factor knock-out mice is that the targeted transcription factors are expressed, albeit at lower levels, in the remaining DC subsets [74, 78].