Characterization of transglutaminase type II role in dendritic cell differentiation and function.

DCs play an essential role in the endotoxic shock, and their profound depletion occurs in septic patients and septic mice. TG2(-/-) mice are more resistant to the endotoxic shock induced by LPS. Here, we studied the cellular and molecular basis of this effect, analyzing the role of the enzyme in DC maturation and function. We show that TG2 is up-regulated drastically during the final, functional maturation of DCs consequent to LPS treatment. In keeping with this finding, the inhibition of the enzyme cross-linking activity determines the impairment of DC function highlighted by wide phenotypic changes associated with a reduced production of cytokines (IL-10, IL-12) after LPS treatment and a lower ability to induce IFN-gamma production by naïve T cells. The in vivo analysis of DCs obtained from TG2(-/-) mice confirmed that the enzyme ablation leads to an impairment of DC maturation and their reduced responsiveness to LPS treatment. In fact, a marked decrease in DC death, TLR4 down-regulation, and impaired up-regulation of MHCII and CD86 were observed in TG2(-/-) mice. Taken together, these data suggest that TG2 plays an important role in regulating the response of DCs to LPS and could be a candidate target for treating endotoxin-induced sepsis.