However, upon incubation of viable immature DC with apoptotic DC followed by LPS treatment, only

20–25% of viable immature DC become CD86+, which is in fact similar to the levels seen in viable immature DC without any LPS treatment (Fig. 4B and C). Furthermore, incubation of viable immature DC with apoptotic splenocytes also resulted in the suppression of LPS-induced subsequent DC maturation. However, the extent of immunosuppression MAPK inhibitor induced by apoptotic splenocytes was not as potent as apoptotic DC (Fig. 4B and C). These results indicate that uptake of apoptotic DC by viable immature DC prevents subsequent upregulation of CD86 in response to LPS. In the absence of inflammatory stimuli, viable immature DC do not produce any IL-12. However, in response to LPS, approximately 22% of cells become IL-12+ (Fig. 4D and E). Similarly, viable immature DC incubated with necrotic DC followed by treatment with LPS show similar proportion of IL-12+ DC. In contrast, viable DC incubated with apoptotic splenocytes followed by LPS treatment showed a slight reduction in IL-12 production, as only 8–11% of the cells became IL-12+. However, viable immature DC incubated with apoptotic DC followed by treatment with LPS failed to induce IL-12, as only 1–2% of DC become IL-12+ (Fig. 4D and E). The uptake of apoptotic

DC by viable immature DC is critically important for the suppression of CD86 upregulation, and IL-12 buy Ku-0059436 induction in response to LPS for no suppression is observed in response to LPS if apoptotic DC and viable DC are separated in culture via transwell (data not shown). In addition to IL-12, DC maturation is also characterized by the upregulation of Smoothened other inflammatory cytokines. In order to assess the effects of apoptotic or necrotic DC uptake by viable immature DC on induction of inflammatory cytokines in response to LPS, we looked at the mRNA expression levels of inflammatory cytokines, including IL-1β (Fig. 5A), IL-6 (Fig. 5B), TNF-α (Fig. 5C), IL-12p35 (Fig. 5D) and IL-12p40 (Fig. 5E). These inflammatory cytokines are expressed at very low levels in viable immature

DC at basal levels. However, in response to LPS, there is massive and rapid induction of these cytokines at mRNA levels (Fig. 5A–E). However, incubation of viable immature DC with apoptotic DC but not necrotic DC suppressed induction of the aforementioned inflammatory cytokines in response to LPS. These findings collectively indicate that the specific uptake of apoptotic DC converts viable immature DC into tolerogenic DC. Next, we looked at the ability of viable DC to prime OVA-specific T-cell proliferation upon apoptotic DC uptake (Fig. 5F). Viable immature DC were incubated with apoptotic or necrotic DC and then pulsed with OVA in the presence of LPS. Then, these were cultured with naïve T cells to assess their ability to induce OVA-specific T-cell proliferation.