IL10 and malaria: Reduced serum levels of IL-10, an important regulatory cytokine, may have triggered an imbalance in the immune response and the worsening of malaria (74–77), contributing to the higher morbidity observed in animals infected with L. amazonensis and P. yoelii. From the standpoint of Leishmania infection, co-infection with P. yoelii increased serum levels of pro-inflammatory cytokines compared to animals infected with Leishmania alone.