SPLEEN DENDRITIC CELLS FROM OLD MICE GENERATE A LOW CYTOTOXIC RESPONSE AGAINST OVA IN YOUNG HOSTS

ZACCA, ESTEFANÍA; CRESPO, MARÍA INÉS; MALETTO, BELKYS; PISTORESI, MARÍA CRISTINA; MORÓN GABRIEL

Congreso; 1º Congreso Franco Argentino de Inmunología. Bs. As.; 2010

During aging, B and T cells manifest changes that affect their response to antigens (Ag). However, it is practically unknown how dendritic cells could participate in these changes. Our previous findings show that in spleen of old mice (18‐20 month‐old) there is a lower content of DCs, which have a lower capacity to activate CD8 T cells than DCs from young (3 month‐old) mice. In this work we analyzed the ability of DCs from old mice to elicit a CTL response in young mice, in order to analyze the ability of DCs independently of the alterations already reported for CD8 T cells during aging. We first analyzed the capacity from old mice to develop a CTL response in vivo. We immunized i.v young and old mice with 2.5x109 latex beads coupled to OVA (B‐OVA) + PolyU/DOTAP and 7 days after immunization these mice were injected i.v with equal proportions of fluorescent‐labeled syngeneic spleen cell populations (a control cell population labeled with 0.5 μM CFSE and an OVA257‐264 peptide‐loaded cell population labeled with 3μM CFSE). One day after injection cytotoxicity was assessed by FACS analysis on total spleen cells. We found significant differences in the percentage of specific lysis in young vs. old mice, 84.3±9.9 vs. 4.7±1.5%, respectively (p<0.05). We also measured IFN‐γ secretion by ELISA in supernatants at the end of 72hs culture after in vitro reestimulation with OVA257‐264 peptide. We found a lower IFN‐γ production in splenocytes from old mice compared to the young ones, 320.5±0.6 vs. 1866.7±1581.5, respectively (p<0.05). To investigate whether this lower capacity from old mice to develop a CTL response in vivo could be due to a lower capacity of DCs from old mice to prime a CTL response in vivo, we immunized i.v young mice with 1x106 purified DCs from spleen of young and old mice incubated with OVA/PolyU/DOTAP. Seven days after immunization these mice were injected i.v with equal proportions of fluorescent‐labeled syngeneic spleen cell populations as previously described. One day after injection cytotoxicity was assessed by FACS analysis on total spleen cells. We found that DCs from old mice have a diminished capacity to prime a CTL response as we observed a lower percentage of specific lysis in old mice compared to the young ones, 40.7±23.2 vs. 88.7±13.4, respectively (p<0.05).