The toll-like receptor 3 ligand polyinosinic-polycytidilic acid (poly(I:C)) has been used as an adjuvant to tumor immunotherapy. The present study aimed to address the impact of poly(I:C) treatment on the natural killer (NK) cells under vaccination or non-vaccination settings. To this end, naïve CD8+Ly5.1+ OT-1 T-cells (1.5×106) were adoptively transferred into Ly5.2 recipient mice. Mice were rested for 24 h after cell transfer and then vaccinated with subcutaneous (s.c.) injection of 100 µg SIINFEKL OVA peptide. Non-vaccinated mice were injected with 100 µl PBS as control. Vaccinated and non-vaccinated mice were then treated with an intra-peritoneal (i.p.) injection of 200 µg of poly(I:C) and 300 µl PBS, respectively. The results showed that poly(I:C) treatment increased the number of the transferred CD8+ T cells in blood, lymph nodes, spleen and liver in vaccinated and non-vaccinated mice at day 3 post-treatment. Poly(I:C) treatment also increased the expression of the NK cell marker NK1.1 on the transferred CD8+ T-cells. Significant increases in the numbers of NK cells were found in the liver after poly(I:C) treatment in vaccinated and non-vaccinated mice. Co-treatment with poly(I:C) at the primary and the secondary vaccination significantly increased the number of NK cells in lymph nodes and liver compartments. Collectively, poly(I:C) treatment in the presence of peptide vaccination increased the number of CD8+ T-cells and NK cells, which may explain the important role of NK cells to CD8 T-cells in general and under vaccination setting in particular.
Key words: TLR3; Immune cells, Adoptive transfer; Poly(l:C), NK cells, Peptides, CD8+ T cells; Vaccination
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