ABSTRACT
Development of partial immunity in people living in malaria endemic area is complex. For better understanding, the lymphocyte subpopulations from infected patients were evaluated by flow cytometer before any antimalarial treatment. In P. vivax infection, the frequency of T-helper type 1 (Th1) was decreased significantly (p = 0.042). In contrast, the number of T- helper type 2 (Th2) was increased significantly (p = 0.001). These trends have also been observed in P. faciparum infection. The Th2 predominant response to the natural malaria infection is likely due to persistent stimulation by Plasmodium species. In P. falciparum infection, CD8+ cytotoxic lymphocytes were significantly reduced (p = 0.007). However, such changes were not found in P. vivax infection. This might suggest that CD8+ cell responses to different Plasmodium spp in a different way. Both Th2 activation and CD8+ cell suppression may reflect less protective effects and chronic malaria infection could be established.