DENDRITIC CELLS ARE RESPONSIBLE FOR THE FAILURE IN CTLs GENERATION IN LSP1-DEFICIENT MICE

ACLAND,R; GROS, M; PASCUAL, M; MALETTO, B; PISTORESI, MC; AMIGORENA,S; MORÓN, G

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencia; 2017

Sociedades de Biociencia

Leukocyte-specific protein 1 (LSP1) is an important regulator ofactin cytoskeleton remodeling, modulating leukocytes motility, dueto its F-actin binding domain. We have previously shown that Lsp1-/- mice have an impaired CTL response after antigen exposure.Moreover, Lsp1-/- dendritic cells (DCs) fail to induce a strong CTLresponse in vivo, migrate to lymphoid tissues, present antigens andproduce IL-12 when transferred into WT mice.In order to deepen the mechanisms operating this diminished CTLgeneration in Lsp1-/- mice, we first analyzed the ability of their CD8+T cells to proliferate and become activated. After in vitro stimulationwith αCD3/CD28, Lsp1-/- CD8+ T cells proliferated and up-regulatedCD25 as strongly as WT CD8+ T cells. Granzyme B production andIFNg release were slightly lower (p<0.05) in Lsp1-/- vs WT CD8+ Tcells, with no difference in IFNg production.Then, we evaluated in vitro activation of CD8+ T cells purified fromOT I (Lsp1+/+) mice after culture with BMDCs (differentiated frombone marrow precursors with Flt3-L), previously pulsed with latexbeads coated with ovalbumin, plus CpG-ODN. Cell proliferation,CD25 up-regulation and IFNg secretion was significantly lower in Tcells cultured with Lsp1-/- BMDCs than with WT BMDCs (p<0.01).Finally, we compared the ability of Flt3L-BMDCs from Lsp1-/- andLsp1+/+ mice to translocate antigen from endosomes to cytosol byperforming the βLactamase export assay. Lsp1-/- BMDCs showed aslower escape of βLactamase to the cytosol, indicating a slower Agtranslocation than in WT BMDCs.In conclusion, these results reveal that the diminished generationof CTLs we observed in Lsp1-/- mice is due to a deficiency in theability of DCs to cross-present Ag rather than a failure in their CD8+T cells. This deficiency in Lsp1-/-DCs is related to an alteration in theescape of the antigen from endosomes to the cytosol, which led tofewer antigens associated to MHC-I to be presented to CD8+ T cells.