The comparative study on the characteristics of Th immune responses in DBA/2 mice infected with different strains of malaria parasites

Objective:To investigate differences of the immune of the responses in DBA/2 mice infected with different strains of malaria parasites.Methods:DBA/2 mice were infected by intraperitoneal injection with 1×106 virulent P.yoelii 17XL-or P.chabaudi AS-parasitized erythrocytes,and then the ratio of RBC infected was counted.Splenocyte IFN-γ and IL-4 producing levels were measured by ELISA.The mRNA expression of T-bet and GATA3,which were Th1 type transcriptional factor and Th2 type transcriptional factor respectively,were measured dynamically by RT-PCR.Results:The expression of T-bet mRNA in both P.y17XL and P.c AS infected mice increased and was higher than that of GATA3,the ratio of T-bet/GATA3 increased significantly in early phase of infection.Both mouse strains showed significant elevation in IFN-γ production followed by significant increase of IL-4 production.In addition,IFN-γ production was much higher in P.c AS-infected mice than in those infected by P.yoelii 17XL which was followed by a momentary increase of IL-4 production.The ratio of T-bet/GATA3 had no trend to decrease until day 8 post-infection(PI).Finally,P.c AS infected mice died with increased parasitemia.In contrast,the ratio of T-bet/GATA3 in P.y17XL-infected mice reached a peak on day 3 PI,and then declined but still kept in a higher level than that in control group.P.y17XL infected mice survived with declined parasitemia.Conclusion:The protective immunity against malaria infection depends on the establishment of effective Th1 and Th2 responses and a successful switch of immune response from Th1 to Th2.The phase and level of immune response might affect the final outcome of malaria infection.