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

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Sociedad Argentina de Inmunología

Leukocyte-specific protein 1 (LSP1) is an important regulator of actin cytoskeleton remodeling, modulating leukocytes motility, due to 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 CTL response in vivo, migrate to lymphoid tissues, present antigens and produce IL-12 when transferred into WT mice.In order to deepen the mechanisms operating this diminished CTL generation in Lsp1-/- mice, we first analyzed the ability of their CD8+ T cells to proliferate and become activated. After in vitro stimulation with αCD3/CD28, Lsp1-/- CD8+ T cells proliferated and up-regulated CD25 as strongly as WT CD8+ T cells. Granzyme B production and IFNg release were slightly lower (p<0.05) in Lsp1-/- vs WT CD8+ T cells, with no difference in IFNg production. Then, we evaluated in vitro activation of CD8+ T cells purified from OT I (Lsp1+/+) mice after culture with BMDCs (differentiated from bone marrow precursors with Flt3-L), previously pulsed with latex beads coated with ovalbumin, plus CpG-ODN. Cell proliferation, CD25 up-regulation and IFNg secretion was significantly lower in T cells cultured with Lsp1-/- BMDCs than with WT BMDCs (p<0.01).Finally, we compared the ability of Flt3L-BMDCs from Lsp1-/- and Lsp1+/+ mice to translocate antigen from endosomes to cytosol by performing the βLactamase export assay. Lsp1-/- BMDCs showed a slower escape of βLactamase to the cytosol, indicating a slower Ag translocation than in WT BMDCs. In conclusion, these results reveal that the diminished generation of CTLs we observed in Lsp1-/- mice is due to a deficiency in the ability 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 the escape of the antigen from endosomes to the cytosol, which led to fewer antigens associated to MHC-I to be presented to CD8+ T cells.