Even cross-presentation capacity, which has been attributed solely to CD8+ cDCs and CD103+ mDDCs in many models, has also been observed in mLCs, CD11b+ mDDCs and/or CD11b+ cDCs [18-26]. In this review we will discuss how underlying limitations of murine experimental models may have led to these apparently contradictory findings. CD11b CD103+ CD11b+ CD103 CD11b CD103 DC subset function

is often inferred from ex-vivo assays that measure the response of antigen-specific T cells co-cultured with DC subsets purified from the draining LNs and/or spleens of immunized or infected mice. Additionally, lymphatic cannulation of larger mammals such as in rats, pigs, sheep and cattle has been used to recover migrating dendritic cells for ex-vivo phenotypical and functional studies https://www.selleckchem.com/products/epz015666.html (reviewed in [27]). T cell proliferation and effector function in these ex-vivo assays generally reflect the extent of antigen presentation at the time of DC harvest, and thus provide an indirect measure of the efficiency of in-vivo antigen uptake and processing by a given DC subset. However, ex-vivo assays

can also be affected by changes in DC immunogenic properties resulting from the physical manipulation involved in DC isolation [28, 29]. In addition, co-culture overrides microanatomical factors that may constrain the probability of in-vivo contact between DCs and T cells within the T cell zones of lymphoid organs. For example, the majority of splenic CD11b+ cDCs are located outside the T cell zone in the steady state and would contact IWR1 T cells only after Toll-like receptor (TLR)-dependent signals

drive their relocation into the T cell zone, yet they may still present antigen oxyclozanide to activate T cells in vitro [30]. In skin-draining LN, the peak arrival of mLCs after immunization is on day 4, compared with days 1–2 for mDDCs [6], so that assays performed on day 2 would not detect the capacity of mLCs migrating from the immunization site to present antigen [31]. Another major limitation of ex-vivo assays is that in-vitro T cell responses do not always mimic their in-vivo counterparts [3, 32, 33]. Effective concentrations of cytokines such as IL-2 are higher in vitro yet T cell division times are longer, and are accompanied by much higher rates of spontaneous cell death [33]. T cell cytokine production tends to be polarized more strongly in vitro than in vivo (reviewed in [34]). Long-term regulation of T cell effector and memory differentiation in vitro is also highly dependent on addition or withdrawal of exogenous cytokines. Most importantly, the conditions that induce T cell deletion in vivo are not replicated effectively in vitro. In-vivo tolerogenic responses to soluble peptide begin with a proliferative burst that is followed rapidly by deletion in the absence of effector cytokine production [33, 35].