Abstract: ObjectiveTo investigate the characteristics of immune response to infection of Plasmodium berghei NK65(P.b NK65)in young and middle aged C57BL/6 mice.MethodsThree weeks and 8 months aged C57BL/6 mice were infected by P.b NK65 parasitized erythrocytes.Flow cytometry was applied to quantitatively analyze myeloid dendritic cells(DCs)and DCs expressing major histocompatibility complex classⅡ (MHCⅡ)or CD86.The levels of interferon gamma(IFN-γ)and interleukin-4(IL-4)in spleen cell supermatants were dynamically detected by enzyme-linked immunosorbent assay(ELISA).ResultsThe number of myeloid DCs(40.08×10⁵)in young aged mice significantly increased 5 days after the infection.The number of myeloid DCs 5 and 8 days after the infection was 103.47×10⁵ and 104.04×10⁵ in the middle aged mice.The numbers of DCs expressing MHCⅡ or CD86 were 50.16×10⁵ and 45.39×10⁵ in young aged mice,and in middle aged mice the numbers were 239.40×10⁵ and 148.48×10⁵,which was markedly more than young aged mice.The level of IFN-γ significantly increased both in young aged(251.01 pg/ml)and middle aged mice(584.17 pg/ml).ConclusionThe cellular and humoral immune responses to infection of P.b NK65 are different between the young and middle aged C57BL/6 mice.