CONICET | Buscador de Institutos y Recursos Humanos

Cathepsin L3 (CL3) is expressed in the juvenile stage of F.hepaticaand has collagenolytic activity, however there is no informationabout its interaction with the immune system. The aim of this workwas to study the ability of CL3 to modulate dendritic cells (DC) activationand its effect on adaptive immune response. DC were differentiatedfrom bone marrow cells of C57BL/6 (WT) or NLRP3 KOmice with GM-CSF and cultured at different times with CL3. DCwere pulsed with recombinant CL3, an inactive variant recombinant(rvCL3) or LPS/ATP. IL-1β and IL-18 secretion were quantified insupernatants by ELISA. Moreover, to study the ability of CL3 to inducea specific immune response, WT mice were intraperitoneallyimmunized with CL3 plus MPLA, three times at 48 h intervals. After 7days of last immunization, lymph node cells (LNC) were recovered,re-stimulated with CL3 and IFN-γ production was studied. Statisticalanalyses were performed by ANOVA. To determine the uptakeof CL3 by DC, we analyzed the presence of labeled CL3 into DC by confocal microscopy. Although after treatment, there was somecolocalization between CL3 with lysosome, the presence of labeledCL3 in the cytoplasm of DC was evident. Besides, CL3 promotesIL-1β and IL-18 production in WT DC, at similar levels than those secretedby LPS/ATP-stimulated DC and this effect was not observedwhen DC were treated with rvCL3. However, when NLRP3KO DCwere treated with CL3, IL-1β and IL-18 secretion were significantlydiminished (p≤0,05). On the other hand, increased levels of IFN-γin CL3 re-stimulated LNC from CL3-MPLA immunized mice wereobserved (p≤0,01).Our results suggest that CL3 up-taking by DC induces IL-1β andIL-18 production-dependent on NLRP3, which in turn was dependenton CL3 enzymatic activity. This event could be related to the uptakeof CL3 that promote the inflammasome activation. The up-regulationof these cytokines may be involved in IFN-γ production.