Th2-like T Follicular Helper Cells Promote Functional Antibody Production during Infection.

CD4 T follicular helper cells (Tfh) are key drivers of antibody development. During malaria in children, the activation of Tfh is restricted to the Th1 subset and not associated with antibody levels. To identify Tfh subsets that are associated with antibody development in malaria, we assess Tfh and antibodies longitudinally in human volunteers with experimental infection. Tfh cells activate during infection, with distinct dynamics in different Tfh subsets. Th2-Tfh cells activate early, during peak infection, while Th1-Tfh cells activate 1 week after peak infection and treatment. Th2-Tfh cell activation is associated with the functional breadth and magnitude of parasite antibodies. In contrast, Th1-Tfh activation is not associated with antibody development but instead with plasma cells, which have previously been shown to play a detrimental role in the development of long-lived immunity. Thus, our study identifies the contrasting roles of Th2 and Th1-Tfh cells during experimental malaria.